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Effects of the Hanging Wall and Footwall on Ground Motions Recorded during the Northridge Earthquake
Abstract
Systematic differences in ground motion on the hanging wall and foot-wall during the Northridge earthquake are evaluated using empirical data. An em-pirical model for the hanging-wall effect is developed for the Northridge earthquake. This empirical model results in up to a 50% increase in peak horizontal accelerations on the hanging wall over the distance range of 10 to 20 km relative to the median attenuation for the Northridge earthquake. In contrast, the peak accelerations on the footwall are not significantly different from the median attenuation over this distance range. Recordings from other reverse events show a similar trend of an increase in the peak accelerations on the hanging wall, indicating that this systematic difference in hanging-wall peak accelerations is likely to be observed in future reverse events.
... However, severe damage to engineering structures in near-fault regions has been observed during recent earthquakes, such as the 1994 Northridge, 1995 Kobe, 1999 Duzce and Chi-Chi, and 2008 Wenchuan earthquakes. The near-fault ground motions can be very different from the far-fault ground motions; they may have the hanging-wall effect, directivity effect, significant vertical ground motion, and large velocity pulses [1][2][3][4][5][6][7][8][9]. Among them, the large velocity pulses of near-fault ground motions aroused considerable attention, which can be very destructive to structures as they usually carry significant seismic energy [10][11][12][13][14]. ...
... Relevant studies can be generally grouped into two categories according to their research topics: (1) comparative studies on the structural response between near-fault pulse-like and far-fault ground motions (e.g., Refs. [15,16]), evaluating the overall influence of the velocity pulses; (2) parametric investigation on the effects of pulse parameters on the structural response (e.g., Refs. [17][18][19][20][21][22]), with particular emphasis on the peak pulse velocity and pulse period. ...
It has been widely recognised that near-fault ground motions can be distinctly different from far-fault ground motions, in terms of their amplitudes and spectral characteristics, and there are a number of studies investigating the effects of near-fault ground motions on the structural response. However, only a few studies focus on underground tunnels, and most of them consider vertically incident seismic waves, neglecting the wave passage effect which is critical for long tunnels. This paper investigates the consequences of near-fault pulse-like ground motions on the seismic tunnel response, with an example of a tunnel embedded in saturated poroelastic soil. The input motions are represented by obliquely incident P1 waves, and the wave passage effect along the longitudinal direction is considered by a 2.5D modelling technique. The seismic tunnel response for near-fault pulse-like and far-fault ground motions is compared. Additionally, artificial ground motions, which have consistent acceleration response spectra with the near-fault pulse-like ground motions, but without velocity pulses, are generated to gain further insight into the contribution of velocity pulses. It is shown that the near-fault pulse-like ground motions can noticeably increase the tunnel internal forces, due to large seismic energy associated with the velocity pulses. For pulse-like ground motions with similar acceleration response spectra, the fling-step velocity pulse can be more detrimental to the tunnel than the forward-directivity velocity pulse. Moreover, the amplification effect of the near-fault pulse-like ground motions on the tunnel internal forces tends to be more prominent for large vertical angles of incidence, highlighting the significance of considering the oblique incidence case for seismic design.
... According to the fault movement, the western section corresponds to the hanging wall and to the active area. This area usually exhibits stronger seismic shaking than the footwall and passive area (Abrahamson and Somerville 1996;Chang et al. 2004;Yuan et al. 2013;Guo et al. 2013). A similar phenomenon was also observed in the 2017 Jiuzhaigou earthquake (Ling et al. 2021). ...
... 14A, 14B, 14C, 14D, 14G, 14H, 15A), especially for the 2008 Wenchuan earthquake. The seismic monitoring of the Wenchuan earthquake indicates that the hanging wall is characterized by stronger shaking than the footwall at the same distance to the seismogenic fault ( Fig. 15B; Abrahamson and Somerville 1996;Chang et al. 2004;Guo and Hamada 2013). Additionally, the landslide-affected area in the hanging wall could extend 20-50 km (Figs. 14 and 15; Xu et al. 2014aXu et al. , 2015Zhao et al. 2020b). ...
On 05 September 2022, an Ms 6.8 (Mw 6.6) earthquake occurred in Luding County, Sichuan Province, China, with an epicenter at 29.59°N, 102.08°E and a focal depth of approximately 16.0 km. Combining field investigations, high-resolution satellite images and multiple datatypes characterizing the seismogenic structure, topography and geology, this study attempts to discuss the influence of geomorphic and tectonic indexes on landslide distribution. The results show that the 2022 Luding earthquake, whose seismogenic fault is the Moxi fault, was a sinistral strike-slip event that triggered at least 4528 landslides over an area of ~2000 km2. These landslides span a total area of 28.1 km2, and the western section of the seismogenic fault, which serves as the active wall area, is characterized by a higher landslide concentration, especially in the Wandong Basin. The seismogenic fault and lithology influence the regional distribution of landslides, and more landslides occurred closer to the seismogenic fault and in the controlling lithologies of granite and dolomite. Local topography influences the landslide occurrence position on the slope; the eastern section is prone to form landslides in the lower gorge section, and the western section is prone to form landslides in the upper-top section of the gorge. For coseismic landslides in the eastern Baryan Har block, the eastern boundary (Longmenshan fault), whose earthquakes are characterized by thrust with slight dextral strike-slip movement, could be the primary landslide-prone area; the southern boundary (Moxi fault; southern segment of Xianshuihe fault), with more intensive strike-slip movement, may be the secondary landside-prone area; and the northern boundary is the tertiary landside-prone area. Additionally, the current landslide inventory may be underestimated, although this underestimation has limited influence on the results.
... Since the concept of "Performance-Based Seismic Design" (PBSD) was introduced by Chandler and Lam [1], accurate and reasonable ground-motion input has become a critical step in the seismic design and reinforcement-and-reconstruction of the structures. In some famous earthquakes, the near-fault area indicates more human casualties and building damage [2] and complex ground motion characteristics, such as directive effects [3,4], fling-step effects [5], velocity pulse effects, and hanging-wall effects [6]. Besides, the 2016 M7.0 Kumamoto earthquake [7] also indicates that near-fault ground motion with a broader frequency band has more complex effects on engineering structures than far-field ones. ...
... Then the up-and down-going wave amplitudes (A r qPm , B r qPm , A r qSVm , B r qSVm , A r SHm , B r SHm ) due to the external loads vector P in each layer can be solved by substituting U into Eqs. (5) and (6). In this way, the displacement-component response (uqP-qSV S,m, uSH T,m and uqP-qSV R,m) of an arbitrary position can be solved. ...
Anisotropic behavior occurs in natural soils and rocks, owing to sedimentation and weathering. However, the semi-analytical methods of near-fault broadband seismogram synthesis in the anisotropic medium are still rare. The physical-based frequency-wavenumber method was constructed for broadband seismogram synthesis due to a kinematic hybrid finite-fault source in a stratified transversely isotropic (TI) half-space for the first time. As the crucial foundation of the seismogram synthesis, the Green's function is established by the dynamic stiffness matrix method, effectively and stably modeling the broadband seismic waves propagation in a TI crust. A hybrid method of the kinematic fault source is applied to reasonably combine the low-frequency deterministic parts with the high-frequency stochastic parts, achieving a broadband waves excitation. The theoretical formulations are well-programmed by the FORTRAN code with OpenMP-based parallel technology to implement the fast solution. Compared with the two published results, the correctness of the methodology is well verified. A numerical example of an Mw7.0 scenario strike-slip earthquake is simulated to discuss the difference between TI and isotropic medium in the aspects: (i) attenuation characteristics near the fault area, (ii) rupture directional effect and velocity pulse, and (iii) response spectrum characteristics.
... Oglesby et al. (1998Oglesby et al. ( , 2000a showed that the normal stress variation gives rise to a larger strength drop on a reverse fault than a normal fault if both faults are under the same initial stress conditions except for the sense of shear. They successfully explained the larger ground motions observed for reverse faults relative to normal faults (McGarr, 1984;Cocco and Rovelli, 1989;Abrahamson and Somerville, 1996) and larger ground motions on the hanging wall than on the footwall, as found for both the 1971 San Fernando earthquake (Nason, 1973;Steinbrugge et al., 1975) and the 1994 Northridge earthquake (Abrahamson and Somerville, 1996) and also as inferred from the locations of precarious rocks (Brune, 2000(Brune, , 2001. Similar results were obtained from 2D lattice models (Shi et al., 1998(Shi et al., , 2003Shi and Brune, 2005) and foam rubber experiments . ...
... Oglesby et al. (1998Oglesby et al. ( , 2000a showed that the normal stress variation gives rise to a larger strength drop on a reverse fault than a normal fault if both faults are under the same initial stress conditions except for the sense of shear. They successfully explained the larger ground motions observed for reverse faults relative to normal faults (McGarr, 1984;Cocco and Rovelli, 1989;Abrahamson and Somerville, 1996) and larger ground motions on the hanging wall than on the footwall, as found for both the 1971 San Fernando earthquake (Nason, 1973;Steinbrugge et al., 1975) and the 1994 Northridge earthquake (Abrahamson and Somerville, 1996) and also as inferred from the locations of precarious rocks (Brune, 2000(Brune, , 2001. Similar results were obtained from 2D lattice models (Shi et al., 1998(Shi et al., , 2003Shi and Brune, 2005) and foam rubber experiments . ...
Dip-slip faulting may juxtapose different geologic materials with different properties, such that a strong material contrast will naturally tend to form. Both the material contrast across a fault and dip-slip motion on a nonvertical fault lead to normal stress variations during earthquake rupture. This normal stress variation will significantly affect dynamic rupture propagation. To demonstrate this, we model dynamic rupture propagation on two-dimensional (2D), reverse, and normal faults (30°, 45°, and 60°dipping) with 20% material contrasts. For predominantly up-dip rupture propagation, we find that normal stress variations due to the free surface and material contrast can either reinforce or counteract each other depending on the configuration. For reverse faults, we find a larger strength drop for a more compliant hanging wall and a lower strength drop for a more compliant footwall. For normal faults, we find a larger strength drop for a more compliant footwall and a lower strength drop for a more compliant hanging wall. For both reverse and normal faults, ground motion will be more symmetric between the hanging wall and footwall with compliant material on the footwall and more asymmetric if more compliant materials are on the hanging wall. Our results have important implications for the dynamics of crustal and perhaps subduction-zone earthquake faulting, where strong bimaterial contrasts across dipping faults are possible. In continental settings, reverse faulting will tend to advect rigid materials from greater depth onto the hanging wall, such that the effects of fault dip and material contrast will counteract one another. In subduction zones, the hanging wall is likely to be more compliant, and hence the material and geometric effects may reinforce one another.
... Although it is difficult to obtain the rupture geometries for all events in our 322 database, it still is obtainable for the larger earthquakes along well-mapped faults. 323 We identified 30 earthquakes with sufficient information from which we could estimate rupture ) at short 346 spectral periods (e.g., Abrahamson and Somerville 1996). In the Sichuan-Yunnan area, most 347 faults have strike-slip mechanisms with high dip angles. ...
The Sichuan-Yunnan area is one of the most seismically active regions in China. As ground-motion models form a key component of seismic hazard analysis, it is important to select (or develop) appropriate models for this area. The increasing number of digital ground-motion records of earthquakes in this area has allowed the development of local ground motion prediction equations (GMPEs). This study compares and, later, recommends appropriate GMPEs for the Sichuan-Yunnan area. We first evaluate the inherent quality of local GMPEs, with respect to their underlying datasets, the variables used and their functional form, to determine a set of candidate GMPEs. Then we investigate how well the predictions from the GMPEs match observations computed from strong-motion records of recent earthquakes in this area. The fit between predictions and observations varies significantly amongst the GMPEs. The results suggest that some recent local GMPEs would lead to biased ground-motion estimates due to limitations of their underlying datasets and functional forms. Based on both evaluations of inherent quality and compatibility with observations, only one local GMPE is recommended. A comparison of the predictions from three widely-used non-local GMPEs indicates that ground motions in the Sichuan-Yunnan area appear more variable than those in other regions but that predictions from these non-local GMPEs are generally unbiased. We recommend use of a mixture of robust local and non-local GMPEs within seismic hazard analyses to capture the epistemic uncertainty in ground-motion prediction for this area.
... As a result, the ground motion at the epicenter and the ground motion in the far area can be significantly different from each other. Depending on the fault size and mechanism, places hundreds of kilometers away from a seismic source may be exposed to seismic ground motion effects [22][23][24][25]. ...
In the past few years, a great deal of work has been done trying to identify the natural phenomenon that characterizes earthquakes and to offer solutions to reduce the resulting damage and costs. These studies have led to important and positive results, but they do not mark the end of people's discussion and scientific demands regarding the complex earthquake phenomenon. Because water reservoirs are near faults, especially residential areas and cities have been built near faults as the primary source of seismic waves. Therefore, the examination of the studies to date will be useful in the evaluation of the civil engineering structures that have been made and are being made. Within the scope of this study, a detailed review of studies on earthquakes of near and far origin is presented. YAKIN VE UZAK KAYNAKLI DEPREMLERİN İNŞAAT MÜHENDİSLİĞİ YAPILARI ÜZERİNDEKİ ETKİSİNE AİT BİR LİTERATÜR İNCELEMESİ ÖZET Son birkaç yılda, depremleri karakterize eden doğal fenomeni tanımlamak ve ortaya çıkan hasar ve maliyetleri azaltmak için çözümler sunmak için çok sayıda çalışma yapılmıştır. Bu çalışmalar önemli ve olumlu sonuçlara yol açmıştır, ancak insanların karmaşık deprem fenomeni hakkındaki tartışmalarını ve bilimsel tartışmalarını sona erdirmemektedir. Su rezervuarları fayların yakınında olduğundan, özellikle yerleşim alanları ve şehirler, sismik dalgaların birincil kaynağı olarak fayların yakınında inşa edilmiştir. Bu nedenle bugüne kadar yapılan çalışmaların incelenmesi, inşa edilen ve yapılmakta olan inşaat mühendisliği yapılarının değerlendirilmesinde faydalı olacaktır. Bu çalışma kapsamında yakın ve uzak kaynaklı depremler üzerine yapılan çalışmaların detaylı bir incelemesi sunulmaktadır. Anahtar Kelimeler: Yakın alan, Uzak alan, Deprem etkisi. 1. Overview of far-and near-fault earthquakes In general, earthquakes that occur in fault zones and in areas close to rupture are called near-field earthquakes or near-fault earthquakes. There is some disagreement among researchers regarding the determination of a specific range in terms of proximity to the breakpoint. For example, some researchers suggest different distances around the fault, ranging from 10 km to 60 km as the near field range. On the other hand, the UBC-97 standard accepts less than 15
... DCS is located on the hanging wall of Xiadian dipping fault (F1). It shows larger, slower attenuation and wider-ranging peak ground velocity than the footwall because of the hanging wall effect (Abrahamson & Somerville, 1996;Oglesby et al., 1998;Pan et al., 2006). Therefore, seismic fortification of engineering structures in FBS and DCS deserves more attention because of the thick loose sediments and amplification effect. ...
Shear‐wave velocity (Vs) structures can reveal the shallow sediment thickness and deep tectonic features of buried faults and geological units. They are important for reducing seismic and geological disasters in urban areas. Based on ambient noise data from the Tongzhou dense array (919 seismographic stations), we obtain a fine shallow‐deep (0–5 km) 3D Vs model, by jointly inverting the phase‐velocity dispersions of Rayleigh waves, including short‐period (0.3–2 s) multimode dispersions using the frequency‐Bessel transform method and the long‐period (2–6 s) fundamental‐mode dispersions using the fast marching method. Our results show that the Vs inhomogeneities agree well with the distribution of geological units. We use the 1 km/s isodepth of Vs as the reference thickness of quaternary sediments. Fengbo sag (FBS) and Dachang sag (DCS), which mainly show low velocity and density, have thick sediment thicknesses (approximately 550–600 and 320–420 m, respectively). The NE high‐velocity belt in Daxing high (DXH) has a thinner sediment thickness (∼230 m). Thus, FBS and DCS have a greater risk of earthquake hazards owing to the strong amplification effects of ground motion. Additionally, Vs distribution in the FBS, DCS, DXH, and Yanshan Fold Belt are spatially related to the medium density and buried faults (Nanyuan‐Tongxian, Daxing, and Xiadian faults). We infer that the Vs structures are associated with the controlling effects of these large normal faults and inhomogeneous strata density. The discontinuity of the NE high‐velocity belt in DXH probably results from the intense tectonic activity of Nankou‐Sunhe fault.
... In this regime, the details of the rupture process and fault geometry become increasingly important. For example, sites on the hanging wall of reverse faults may experience particularly severe ground motions (Abrahamson & Somerville, 1996;Chang et al., 2004;Oglesby et al., 2000). Normal faulting events, in contrast, may feature substantially lower ground motions, particularly at sites on the footwall (Brune, 2000;Brune & Anooshehpoor, 1999). ...
On 8 July 2021 a M6.0 normal faulting earthquake rocked the community of Walker and the surrounding region near the California‐Nevada border. In the 1990s, field surveys of nearby Meadowcliff Canyon identified numerous precarious rocks deemed likely to topple in the event of strong shaking. Despite their proximity (∼6 km) to the 2021 earthquake, the precarious rocks still remain standing. In this work, we combine advanced source and ground motion characterization techniques to help unravel this mystery. High‐precision hypocentral locations reveal a clear north/south‐striking, east‐dipping rupture plane along the southern extension of the Slinkard Valley fault. The mainshock nucleated near the base of the fault, triggering thousands of aftershocks. Bayesian source spectral analyses indicate that the mainshock had a moderately‐high stress drop (∼17 MPa), and that aftershocks with deeper hypocenters have higher stress drops. Peak Ground Acceleration (PGA) recordings at regional stations agree well with existing ground motion models, predicting PGA of ∼0.3 g in Meadowcliff Canyon, a level sufficient to topple precarious rocks based on PGA‐derived stability criteria. We demonstrate that despite these large ground accelerations, the pulse duration in Meadowcliff Canyon is too short to supply the impulse necessary to damage these features, observations which support the application of dynamic toppling models that account for the joint effects of pulse amplitude and duration when assessing rock fragility. This study provides a unique vantage point from which to interpret rarely‐observed strong‐motion recordings from close to an active normal fault, one of many that dominate hazard along the eastern Sierra.
... The average R HYP distance for a site located on the HW region is less than the average R HYP distance for a site located on the FW region when both sites have the same R JB or R HYP distances. Therefore, the site located on the HW region experiences larger ground motions compared with the other site located on the FW region (Abrahamson and Somerville, 1996;Donahue and Abrahamson, 2014). The mean R HYP distance for a particular azimuth angle of θ, < R HYP > θ , is obtained by averaging over all R HYP distances. ...
... We divided the effects of seismogenic faults on landslides into two modes to study the spatial pattern of EQTLs and fault geometry: (1) The faults were divided based on the difference in fault geometry and spatial distribution state and (2) the vertical fault direction was divided into hanging wall and footwall based on the difference in ground motion propagation on both sides of the fault. Several studies have found that ground motion on the hanging wall of an angled fault is stronger than that on the footwall during earthquakes (Abrahamson and Somerville 1996;Yu and Gao 2001;Ulusay et al. 2004). The results (Fig. 7) show that as fault dip angle increases, the number and distribution range of landslides in the direction perpendicular to the fault gradually decrease. ...
Earthquake-triggered landslides (EQTLs) are affected by both seismogenic faults and topography. Using landslide data associated with the 2008 MW7.9 Wenchuan earthquake, the distribution characteristics of EQTLs were identified. And the influence of topographical changes and fault dip angle changes on the distribution of EQTLs was analyzed. Fault dip angle had a controlling impact on EQTL spatial distribution. When the dip angle increased, EQTL distribution was concentrated in a certain range on both sides of the fault and decayed rapidly with distance from the fault. When dip angle decreased, the hanging wall effect became more obvious, and the number of landslides on the hanging wall gradually decreased with distance from the fault. In terms of topography, EQTLs were closely related to relative elevation differences, forming a single peak for a local relief range of 400–1600 m. For > 70% of statistical units, EQTL density increased with local relief; the landslide distribution conformed to an exponential relationship with relief. Peak local relief and dominant local relief were highly negatively correlated with fault dip angle. Fault geometry and motion characteristics control the propagation of seismic waves, directly affecting the distribution of EQTLs; moreover, as tectonic activity controls local relief, it also indirectly affects the distribution of EQTLs. Our findings provide empirical evidence for the rapid assessment of EQTL distributions.
... Bommer et al. (2003) suggested that normal faults produce lesser (<%5) ground acceleration under identical earthquake parametres and ground conditions. However, the hangingwalls in reverse faulting events experience up to %50 elevated ground shaking (Abrahamson and Somerville, 1996). In the present study, we used a domestic GMPE by Ulusay et al. (2004) that relies a relatively long and dominantly strike-slip fault dataset including the large earthquakes such as 1999 Kocaeli earthquake (Mw7.4). ...
Although the North Anatolian Fault is one of the most investigated continental transform faults across the globe, the maximum earthquake magnitude (Mmax) expected and the resulting seismic risk to the nearby big settlements is still a matter of debate. Some part of the problem issues from the relatively short paleoseismological record of this fault while the rest is closely related to the uncertainties of probable multiple segment ruptures. This study addresses this issue through the investigation of the Sünnet-W landslide in terms of age and dynamic triggering conditions in NW Anatolia where similar large bedrock failures abound. This landslide is a rotational failure with a volume of 5.75 million m3 and developed in the Jurassic-Cretaceous carbonate successions 16 km off the NAF. Radiocarbon dating of the earliest sediments of the associated dam lake upstream yields a calibrated age of 8000±35 yr BP for the landslide formation. Pseudo-static back analysis of the failure based on the pre-slide morphology, strength, and discontinuity density of the bedrock revealed horizontal accelerations of 0.484g and 0.976g for the initiation of failure. The steep topography and especially the height of the failed slope imply that a topographic amplification of 1.5 times would be reasonable based on the previous numerical models. Moreover, the paleoclimatological conditions of the time are estimated not to be sufficient for the complete saturation of the deep sliding surface. Even after the consideration of these site-specific encouraging conditions, a threshold magnitude of about 8.0 for the triggering earthquake of the Sünnet-W landslide is suggested. This estimate is at least six times larger than the anticipation of the previous paleoseismological studies (M7.4) from the western part of the NAF. We suggest that the triggering earthquake of the Sünnet landslides 8 ky ago may have been a huge cascade rupture that involves many, if not all, of the segments between Erdek and Niksar along the western and central NAF. This type of multi-segment rupture was previously conceptualized throughout the NAF but remained unexemplified up to date. The present study demonstrates that they should be seriously traced in far-reaching paleoseismological records due to their huge impacts on the seismic hazard of the region.
... It has been seen that the ground motion characteristics in the vicinity of an active fault are different from the ground motions recorded far from the fault. Ground motion characteristics in a near-fault region are highly dependent on the earthquake's fault type, magnitude, rupture mechanism, and position relative to the strike direction of the fault [47][48][49][50]. The major characteristics of a near-fault ground motion include the presence of significant vertical ground motion component, directivity effect, fling step effect, long period velocity pulses of high amplitude, and hanging wall effect. ...
An improved formulation of the horizontal shear behavior of the unbonded fiber-reinforced elastomeric isolators (UFREI), which predicts both the pre-rollover and the post-rollover behavior considering the effect of the vertical load, is proposed. A simplified and computationally inexpensive formulation of the horizontal shear behavior of the UFREI has also been proposed afterward. Further, these formulations are verified using experimental results and compared with the results obtained using the other earlier methods in the recent literature. The horizontal shear behavior predicted by both of the proposed formulations is observed to fit the experimental results very well. The shear behavior predicted by these formulations is observed to be more accurate than the corresponding predicted by the other formulations from the recent literature. A parametric study characterizing the effect of the vertical pressure and the initial elastomeric shear modulus on the horizontal shear behavior of isolators is also carried out. The proposed formulations are further used to model the behavior of the UFREI employed to isolate the benchmark structure considered in the study.
Supplementary damping devices are further installed alongside the nonlinear UFREI isolation system to mitigate the excessive displacement demand on isolators under near-fault ground motions. The isolated benchmark structure is thus coupled with a Magneto-rheological Damper (MRD) with an improved control algorithm for nonlinear isolation systems in three configurations, i.e., semi-active, passive-on, and passive-off. A comparative study of these configurations shows that MRD in passive-on mode provides the minimum isolators displacement response, but an overall improved structural response is achieved with MRD in the semi-active mode of operation.
... In general, the near-fault earthquakes are seismic events with a ruptured fault distance not exceeding 10 km (Mavroeidis 2003) to 20 km (Bray and Rodriguez-Marek 2004). Furthermore, the near-fault earthquakes have special characteristics, including the effects of hanging wall and footwall (Abrahamson and Somerville 1996), ruptured fault directivity (Bray and Rodriguez-Marek 2004;Howard et al. 2005), and velocity pulse (Farid Ghahari et al. 2010). Through the investigation of Parkfield ground motion, recorded on June 27, 1966, which caused severe damages to adjacent structures as it was a near-fault pulsetype ground motion, Housner and Trifunac (1967) concluded that the design of important structures, under the risk of ground motions similar to Parkfield earthquake event, requires special attention. ...
Based on an innovative high-speed railway simply supported bridge (HSRSSB) model, the potential influence of near-fault pulse-type ground motions on HSRSSB is analyzed. Eighty-five original records of such ground motions are imposed on the simulation model. The dynamic responses of the bridge are calculated, including girder displacement, rail displacement, pier bending moment, bearing deformation, and residual displacement. Linear regression analysis reveals the relationship between the dynamic response and intensity measures (IMs). Moreover, six typical ground motions are chosen from these eighty-five records as prototypes in order to perform a pulse parameter analysis. Through an artificial ground motion synthesis, the effects of parameters, such as pulse amplitude, pulse period, and pulse number, on the behavior of HSRSSB are investigated and discussed. It is concluded that the response of HSRSSB depends on the acceleration-type IMs and presents a strong linear relationship with spectral IMs at the fundamental period of the structure. Regarding the pulse parameters, the HSRSSB dynamic response shows a positive correlation relationship with pulse amplitude, but a negative correlation with pulse period.
... Northridge earthquake (Dreger, 1994;Abrahamson and Somerville, 1996;Somerville et al., 1996), since earthquake directivity was combined with the effects of the finite size of the fault. Over the years, with the development of the broad-band seismic networks, the data quantity and quality have improved considerably. ...
Rupture directivity and its potential frequency dependence is an open issue within the seismological community, especially for small‐to‐moderate events. Here, we provide a statistical overview based on empirical evidence of seismological observations, thanks to the large amount of high‐quality seismic recordings (more than 30,000 waveforms) from Central Italy, which represents an excellent and almost unique natural laboratory of normal faulting earthquakes in the magnitude range between 3.4 and 6.5 within the time frame 2008–2018. In order to detect an anisotropic distribution of ground motion amplitudes due to the rupture directivity, we fit the smoothed Fourier Amplitude Spectra (FAS) cleared of source‐, site‐ and path‐effects. According to our criteria, about 36% of the analyzed events (162 out of 456) are directive and the distribution of rupture direction is aligned with the strikes of the major faults of the Central Apennines. We find that the directivity is a band‐limited phenomenon whose width may extend up to five times the corner frequency. The results of this research provide useful insights to parameterize directivity, to be explicitly implemented in future ground motion modeling and scenario predictions.
... Similarly to field observations and numerical models (e.g., Abrahamson & Somerville, 1996;Allen et al., 1998;Chang et al., 2004;Nason, 1973;Shin & Teng, 2001;Steinbrugge et al., 1975) and numerical models (e.g., Duan & Oglesby, 2005;Ma & Beroza, 2008;Oglesby & Day, 2001;Oglesby et al., 1998Oglesby et al., , 2000Scala et al., 2019;Shi et al., 1998), the experimentally observed surface motions during the interaction of the supershear rupture and the trailing Rayleigh with the free surface show substantial asymmetry between the hanging wall and footwall, with the hanging wall experiencing larger velocity magnitudes. However, as a result of the nearly vertical motion of the hanging-wall and right-downward motion of the foot wall (with temporal sub-horizontal motion during for the trailing Rayleigh; Figures 6-8), the footwall generally show larger horizontal velocity than the hanging wall ( Figure 13) for the dip angle of β = 61° considered in our experiments. ...
We study how the asymmetric geometry of thrust faults affects the dynamics of supershear ruptures and their associated trailing Rayleigh ruptures as they interact with the free surface, and investigate the resulting near‐field ground motions. Earthquakes are mimicked by propagating laboratory ruptures along a frictional interface with a 61° dip angle. Using an experimental technique that combines ultrahigh‐speed photography with digital image correlation, we produce sequences of full‐field evolving measurements of particle displacements and velocities. Our full‐field measurement capability allows us to confirm and quantify the asymmetry between the experimental motions of the hanging and footwalls, with larger velocity magnitudes occurring at the hanging wall. Interestingly, because the motion of the hanging wall is generally near‐vertical, while that of the footwall is at dip direction shallower than the dip angle of the fault, the horizontal surface velocity components are found to be larger at the footwall than at the hanging wall. The attenuation in surface velocity with distance from the fault trace is generally larger at the hanging wall than at the footwall and it is more pronounced in the vertical component than in the horizontal one. Measurements of the rotations in surface motions confirm experimentally that the interaction of the rupture with the free surface can be interpreted through a torqueing mechanism that leads to reduction in normal stress near the free surface for thrust earthquakes. Nondimensional analysis shows that the experimental measurements are consistent with larger‐scale numerical simulations as well as field observations from thrust earthquakes.
... The significant hanging-wall/footwall effect may aggravate the damage of structures (Sapkota et al. 2013). The hanging-wall ground motion has large acceleration peaks and high input energy, which amplifies the ground motion during propagation (Abrahamson 1996). Many studies can be found focusing on the effects of near-fault ground motions on civil structures, such as buildings, tunnels and bridges (Aghamolaei et al. 2021;Xie and Sun 2021;Abd-Elhamed and Mahmoud 2019;Faherty et al. 2022;Bedon, Rinaldin, and Frgiacomo 2015;Bedon et al. 2019;Shehata, Mohamed, and Tarek 2014;Hadianfard and Sedaghat 2013). ...
This study aims to quantify effects of hanging wall/footwall fault parameters on dynamic responses of base-isolated and base-fixed ancient timber buildings. Finite element models of a real timber building named Xi’an Bell Tower with and without isolation technology are firstly built and verified by comparison with existing literatures and criterion. Fitting analysis of three typical models, Abrahamson-Silva-Kamai, Campbell-Bozorgnia and Chiou-Youngs models, as well as 622 recorded ground motions is then conducted to determine the optimal model to generate earthquake waves of this study. Finally, effects of hanging-wall/footwall fault parameters on structural seismic performance of the based-isolated and base-fixed ancient timber buildings are investigated in details. The results show that Abrahamson-Silva-Kamai model achieves the best fitting results with the lowest computational errors. Isolation technology can improve seismic performance significantly for ancient timber buildings with different ages. Isolation effectiveness of the base-isolated models decrease with increasing building ages in different fault parameters. The isolation effectiveness remains unchanged with different fault dip angles in footwall earthquakes, whereas it decreases with the increase of fault dip angles in hanging-wall earthquakes at the same site distance. The smaller the absolute sit distances are, the better the IE in the same fault dip angle is. The structural isolation effectiveness in hang-wall earthquakes is better than that in footwall earthquakes.
... 8 This situation typically occurs within few dozen kilometres from a seismic source, in the socalled near-field or epicentral area where, depending on fault dimension and rupture mechanism, specific ground motion effects can occur. [9][10][11][12] Since the pioneering work by Housner and Trifunac 9 it has been recognised that in the near-field domain engineering structures can be exposed to seismic demands that are much different from those arising from far-field domain, which correspond to the typical demands that influence the design of the structures, both in terms of intensity and, especially, of nature of ground motion. 13 The vertical component of ground motion typically focuses its energy in a high frequency band (commonly above 5 Hz 13 ) and, within 5 km from the source, the peaks of vertical and horizontal components can be considered to occur almost simultaneously. ...
Recent observations of failure and damage of buildings and structures under seismic action has led to an increasing interest for an in-depth analysis of the vertical component of site ground motion. In particular, when dealing with saturated soils, the current engineering practice does not usually go beyond the simplified u– p formulation of the Biot's equations describing the coupled hydro-mechanical behaviour, thus neglecting some terms of fluid inertial forces, despite the presence of more refined formulations, for example, the u– U formulation. Therefore, a theoretical and numerical validation of the u– p formulation as compared with the u– U formulation is proposed in this work, where the numerical simulations are compared with the analytical solution for the u– p formulation, which is also derived and illustrated in this text. The comparison between the two formulations and the analytical solution is provided for different levels of permeability and dynamic actions, which are representative of a wide scenario of site ground properties and seismic hazard in the vertical direction. In particular, the soil response is analysed in terms of acceleration and pore pressure time history, frequency content, acceleration response spectrum, and amplification ratio of acceleration. This study extends the discussion of the limits of applicability of the u– p formulation with respect to the rigorous solution of Biot's equations (obtained here with u– U formulation) to the context of a complex dynamic regime provided by the vertical components of real earthquake records, and paves the way for further investigations.
... The Wenchuan earthquake was a complex seismic source rupture process on a seismogenic fault with a rupture length above 300 km. This violent earthquake provided a strong ground motion energy source during landslide formation with high amplification effects, and the hanging wall effects (Abrahamson and Somerville, 1996;Huang and Xu, 2008;Liu and Li, 2009;Lu et al., 2013) of the nearby Shikan fracture thrust may have contributed to the strong ground motion and landslide or other disasters in the study area. ...
The Wenchuan earthquake triggered many landslides in the Longmen Mountain area. Among them, landslide #1, which had a unique failure model, occurred in the Liujiawan area, Qingchuan County, and experienced two failure processes. First, the shallow surface phyllitic slate and slate generated coseismic landslides, and then, the outcropping dolomite generated another landslide accumulation process at the slope foot. Landslide deposits formed a two-stage accumulation platform with different lithologies, and this structure was extremely rare among large coseismic landslides triggered by the Wenchuan earthquake. The numerical simulation results verified the unique failure process of landslide #1. The study results are helpful in further understanding landslide disasters caused by strong earthquakes and the disaster formation process.
... and the closest distance to the fault rupture area, rup R , (ii) a nonlinear site-response model involving a continuous site soil characterization through the parameter, VS30, (iii) a model for considering whether the site is on the hanging-wall or foot-wall side, as sites on the hanging-wall side experience larger motions (Abrahamson and Somerville[87]), (iv) a model for dependence on the depth to the top of fault rupture plane, as the buried ruptures lead to larger short-period ground motions (Somerville and Pitarka[88]), (v) a model for large-distance attenuation in the case of moderate earthquakes (i.e., when rup R > 100 km), and (vi) a model for amplification due to the depth of soil at the site, which is characterized by 1 0 Z , i.e., the depth at which shear wave velocity attains a value of 1.0 km/s. It also incorporates three terms with flags to differentiate between the types of faulting (i.e., reverse, normal, and strike-slip). ...
The northwest region of India is prone to very high level of seismic hazard due to the presence of the western Himalayan plate boundary within the region. To manage and mitigate the associated risk in an effective manner, it is necessary to have reliable and realistic mapping of seismic hazard in the region. This study presents a comprehensive seismic hazard analysis to prepare the probabilistic seismic hazard maps of northwest India in terms of 5%-damping spectral accelerations at different natural periods for rock-type site conditions in a significant updating of the results of the previous studies. Major improvements made in the present study include: use of non-uniform spatial distribution of the expected seismicity over each of the 16 area sources of shallow crustal earthquakes considered, consideration of the additional effect of deep focus earthquakes in Hindukush subduction zone by modeling this as a dipping plane source, selection of the most appropriate ground motion prediction equations (GMPEs) for both types of seismic sources by using the available strong motion data, and estimation of the source-to-site distance metrics consistent with the selected GMPEs. An empirical approach, based on a detailed seismic hazard analysis for different soil conditions, is also proposed to obtain realistic amplification factors for modifying uniform hazard response spectra for the rock sites to those for the soil sites with a given 30 S V value. A critical comparison of the results of this study with those of the major past studies indicates large discrepancies and differences, which could be attributed to several unrealistic and subjective assumptions and idealizations made in the past studies. Finally, on comparing the present estimates with those prescribed by the Indian code IS 1893 (Part-1), it is found that one additional zone of greater hazard level may need to be introduced in the code. A simple modification involving the MCE-level hazard estimates for peak ground acceleration and 0.2-s spectral acceleration is also proposed in the Type-I spectral shape prescribed by the Indian code in order to raise the hazard levels for non-rigid structures.
... Even today, seismic records greater than magnitude 7 in areas less than 20 km away from faults are very valuable. According to the analysis of near-fault strong earthquake observation data, the inversion of seismic source process and numerical simulation of near-fault ground motion found mainly has the characteristics of nearfault ground motion [21][22][23][24][25]: (1) concentration of near-fault strong ground motions; (2) surface rupture and fling-step; (3) rupture forward directivity effect; (4) large velocity pulse; and (5) hanging wall [26]. It was found that the most prominent feature of near-fault seismic was velocity pulse, which was mainly created by near-fault seismic forward directional and slip effects [27][28][29]. ...
Abstract Reinforced concrete frame‐bent structures are one of the structural forms commonly used in industrial factory buildings. In order to study the seismic behaviour of frame‐bent structures located near fault areas, eight pulse‐like, eight non‐pulse near‐fault motions and eight far‐fault ground motions have been selected in this paper. The finite element model of a reinforced concrete frame‐bent structure was established to study seismic responses to near‐fault and far‐field ground motions. Numerical analysis results indicate that the maximum base shear of the structure under the action of near‐fault ground motion was 5.10 times that of far‐fault and 1.47 times that of non‐pulsed near‐fault ground motion; the maximum story drift angle under pulse‐like near‐fault ground motion was 3.8 times that of non‐pulse and 19.7 times that of far‐fault ground motion. Therefore, engineering designers should pay more attention to the seismic performance of frame‐bent structures under the action of near‐fault ground vibration.
... The fault projection is indicated by solid lines. The spatial division of the hanging wall (HW) and foot wall (FW) is illustrated by the dashed lines(Abrahamson and Somerville 1996). Joyner-Boore distance and name of the station are marked in the low-right corner of each panelFig. ...
A moderate magnitude earthquake with M w 5.8 occurred on June 17, 2019, in Changning County, Sichuan Province, China, causing 13 deaths, 226 injuries, and serious engineering damage. This earthquake induced heavier damage than earthquakes of similar magnitude. To explain this phenomenon in terms of ground motion characteristics, based on 58 sets of strong ground motions in this earthquake, the peak ground acceleration (PGA), peak ground velocity (PGV), acceleration response spectra (Sa), duration, and Arias intensity are analyzed. The results show that the PGA, PGV, and Sa are larger than the predicted values from some global ground motion models. The between-event residuals reveal that the source effects on the intermediate-period and long-period ground motions are stronger than those on short-period ground motions. Comparison of Arias intensity attenuation with the global models indicates that the energy of ground motions of the Changning earthquake is larger than those of earthquakes with the same magnitude.
... To quantitatively evaluate the applicability of the NGA-West2 models to this event, the residual analysis method proposed by Abrahamson and Somerville (1996) was used to separately analyze the residuals of the logarithm of the ratio of the observed data relative to the estimates from the BSSA2014 model. Figure 5 shows the variations in the intraevent residuals with R rup for the observed PGAs, PGVs, and SAs at T 0:2, 0.5, 1.0, 2.0, 3.0, and 5.0 s from the original and residual ground motions, which are corrected relative to the bedrock site (V S30 760 m=s) by the SS2014 model. ...
Pulse-like ground motions cause severe damage in structures at certain periods. Hence, pulse effects need to be considered during probabilistic seismic hazard analysis and seismic design in the near-fault region. Traditional ground-motion models used to quantify the hazard posed by pulse-like ground motions may underestimate them, but they are relatively suitable for describing the residual ground motions after extracting pulses. Nevertheless, the applicability of Next Generation Attenuation-West2 Project (NGA-West2) models to pulse and residual ground motions has not been evaluated. Moreover, the applicability of recently developed directivity models, including the Shahi and Baker (2011; hereafter, SB2011), Chang et al. (2018; hereafter, Chang2018), and Rupakhety et al. (2011; hereafter, Rupakhety2011) models, has not been investigated for this event. Here, based on the abundance of pulse-like ground motions recorded during the Mw 6.4 Hualien earthquake, the applicability of NGA-West2 models and directivity models was quantitatively evaluated. In summary, (1) The applicability of NGA-West2 models to the observed original and residual ground motions varies significantly at different periods. The suggests that NGA-West2 models overestimate the original and residual ground motions for short periods (T<1.0 s), but are suitable for describing the residual ground motions yet underestimate the original ground motions for long periods (T≥1.0 s). (2) Pulse periods and amplification bands due to pulses are unusually larger than previous events. Similar to the Chang2018 model, the plateau of this event starts and ends at the periods of 0.70 and 1.1 times the pulse period. However, the Chang2018 and SB2011 models underestimate the constant ordinate of this plateau. Spectral ordinates of the spectral shape curve due to pulses for the short period (∼Tn<1.3 s) are smaller than the predictions from the Rupakhety2011 model. The trend was reversed for long periods (∼Tn>3.0 s). Compared with the Rupakhety2011 model, the peak location of the spectral shape curve is shifted to the long period. These results will be helpful for updating these models in the near future.
... The critical horizontal seismic acceleration a c calculated through pseudostatic analysis showed mean values around 0.62 g for R u = 0 and 0.54 g for R u = 0.1. These values are consistent with the generalized distribution and clustering of large landslides along the mountain fronts of the hanging walls that compose the main thrusts of Precordillera (Junquera-Torrado et al. 2019), where the greatest seismic accelerations are recorded by the hanging wall effect (Abrahamson and Somerville 1996). It is known that pseudostatic analysis has some drawbacks. ...
A total of 36 rock slides were selected for analysing a probable seismic source in the active Andean Precordillera (31°–33°S), the most seismic region of Argentina. Seven of these slope instabilities were selected for in-depth analysis in the field as a function of the most frequent class, lithological susceptibility and field accessibility. Reconstructing the topography previous to collapse and using geotechnical parameters extracted from field data in conjunction with geomechanical testing, the rock slides were modelled using pseudostatic limit equilibrium analyses for the obtention of the critical probabilistic acceleration (\({a}_{c}\)) required to generate the instability under unsaturated conditions and considering both the horizontal and vertical seismic components. To perform a probabilistic estimation of \({a}_{c}\), the parameters in relation to the generalized Hoek–Brown failure criterion were selected to operate statistically using 2D SLIDE 8.0 software. Applying inversely Ground Motion Prediction Equations (GMPEs) and concerning the distance to the studied paleolandslide, a possible earthquake inducing a seismic coefficient (\(k_{h}\)) ≥ \(a_{c}\) was determined. Therefore, a near active fault(s) capable of generating an earthquake magnitude inducing a Peak Ground Acceleration (PGA) ≥ \({a}_{c}\) at the paleolandslide location was designated as the possible seismogenic source of the slope instability. Intersecting these results, potential paleoseismic events which could have caused several slope instabilities were determined. Thus, a new methodology was developed, which allowed to determine the main seismogenic sources capable of inducing the modelled instabilities in each studied subarea in the Precordillera.
... Although most of these pulses are observed from the radiation pattern of the fault oriented in the fault-normal direction, the fault parallel direction could result in strong pulses, too [13], [14]. Fling-step effect is the relative slip between the hanging wall and footwall which produces large amplitude unidirectional velocity pulse and a monotonic step in displacement time history [15], [16]. These pulses result in the occurrence of static permanent ground displacements due to tectonic deformation associated with fault rupture [17]. ...
On October 23, 2011 an earthquake occurred approximately 20 km north of the province of Van,Turkey with a magnitude of Mw 7.2. Following the main earthquake, 111 aftershocks withmagnitudes of 4.0 and above occurred. The state of damage was very severe and considerableamount of unreinforced masonry buildings were affected highlighting the need for investigating theseismic design of unreinforced masonry buildings in the affected area. In this paper, seismicbehaviour of a two story masonry building designed according to the Turkish Building Seismic Code2018 is presented. The main objective of this activity was to study the near field and far field syntheticground motions, artificial ground motions and evaluating the responses to get reliable information onthe seismic response of masonry buildings.
... 5, it is evident that the average PGA values recorded on the hanging wall stations are higher compared to those on the footwall stations. Although this observation is reinforcing the existing literature [19,20,21,22,23], there are also exceptions for this trend at some stations. Apart from the comparison of PGA values on hanging wall and footwall stations, another explicit comparison that can be made is that the PGA values in the FP direction are higher than those in the FN direction at both the sets of stations. ...
Structural engineering involves clear understanding of characteristics of ground motion used in the design of structures to identify the critical aspects of their behavior. Peak amplitude of response (a, v, or d), predominant frequency and duration of strong ground motion are the most important parameters of ground motion that are required for this purpose. These parameters are influenced by the source, path and site conditions. However, it is also found that for the same distance these characteristics are highly sensitive to the fault direction and the side on which the site lies i.e., hanging wall or foot wall. In this paper, a case study is performed to understand the influence of fault direction and location of site on the characteristics of the ground motion. For this purpose, 371 ground motions recorded during 1999 Chi-Chi, Taiwan earthquake are selected. Initially, these ground motions were arranged in terms of fault parallel and fault normal direction and also according to distance from the fault. Later, ground motion characteristics were obtained using standard procedures. From the above, it was found that, in the near-fault region, PGA and PGV on the hanging wall are higher by at-least 20% than that on the footwall. From this observation, the near-fault region can be defined not by using the distance from the fault, but by observing the ratio of PGA values in fault normal and parallel directions. This method of estimating the near-fault region is reliable because the hanging wall effect is caused only due to the inclined dip-angle of the fault which is inevitable in most of the thrust and normal faults.
... The hanging wall effect is one of the most important characteristics of NF ground motions, especially for reverse faults (Abrahamson and Somerville 1996). Typically, the hanging wall is closer to the epicenter, and multiple reflections occur between the ground surface and the fault plane (Shabestari and Yamazaki 2003). ...
Observations from several earthquakes indicate that near-fault (NF) ground motions have a significant influence on the seismic response of structures. However, existing studies have only discussed the influence of a certain NF characteristic on the seismic response, rather than systematically discussing and comparing the influence of different NF characteristics. Furthermore, current research is only suitable for a specific structure while the influence of NF characteristics on structures with different dynamic characteristics has not been revealed. As an important lifeline project, the safety of a cable-stayed bridge (CSB) during earthquakes is of great concern. Therefore, this paper investigates the influence of NF ground motions on the seismic response of CSB. Firstly, three major characteristics (i.e., the hanging wall effect, rupture directivity effect and high velocity pulse) of NF ground motions are analyzed using NF records of the Chi–Chi earthquake. Secondly, a finite element (FEM) model for modeling a prototype CSB is developed and benchmarked. Then, the seismic responses of the prototype CSB subjected to NF ground motions with different characteristics are analyzed using the benchmarked FEM model. The analyses show that hanging wall effect, rupture directivity effect, and high velocity pulse affect the seismic demand of the CSB to varying degrees. Furthermore, the influences of NF characteristics on the displacement response of CSBs with different fundamental periods are investigated using SDOF systems. The analysis results show that different NF characteristics have various influences on the displacement response of CSBs with different fundamental periods.
... Internal prism deformation can generate oversteepened slopes prone to slope failure Lackey, Moore, Strasser, Kopf, et al., 2018;Strasser et al., 2011). Coseismic rupture of a fault, such as the MSF (Figures 1 and 2), can amplify ground shaking within the hanging wall (Abrahamson & Somerville, 1996) and lead to slope failure. This mechanism has been suggested for Nankai and other splay fault systems (e.g., Baba et al., 2006;Plafker, 1972;Strasser et al., 2011;Tanioka & Satake, 2001). ...
Three‐dimensional (3‐D) seismic reflection data and sediment cores record ~2.87 million years of structural and depositional history of a trench slope basin along the outer Nankai accretionary prism, southwest Japan. Numerous mass transport deposits (MTDs) and fault structures are present in the basin. Here, we investigate the links between slope failures, slope basin development, and movement along a prominent out‐of‐sequence thrust (OOST) fault and development of a large anticline. Three two‐dimensional (2‐D) cross sections are restored to ~2.2 Ma using stratigraphic and structural relationships interpreted in the 3‐D data. The restorations are then compared and combined to provide a 3‐D perspective of basin development. We find that total shortening across all faults and folds was accommodated by different displacement styles along multiple branches, with 5.3, 5.5, and 7.3 km of shortening from northeast to southwest over the past ~2.2 Ma. We believe that the majority of this displacement occurred prior to ~1.7 Ma, followed by a dramatic decrease in slip rate within the study area as slip was transferred to the more seaward portions of the prism. In the northeast, deformation is primarily accommodated by the main branch of the OOST and anticlinal faulting, while deformation in the southwest is primarily along deeper branches of the OOST. This differential motion explains the occurrences of various mass wasting events, and lateral differences in trench slope basin geometry within the study area.
Subduction forearcs are subject to seismic hazard from upper plate faults that are often invisible to instrumental monitoring networks. Identifying active faults in forearcs therefore requires integration of geomorphic, geologic, and paleoseismic data. We demonstrate the utility of a combined approach in a densely populated region of Vancouver Island, Canada, by combining remote sensing, historical imagery, field investigations, and shallow geophysical surveys to identify a previously unrecognized active fault, the XEOLXELEK‐Elk Lake fault, in the northern Cascadia forearc, ∼10 km north of the city of Victoria. Lidar‐derived digital terrain models and historical air photos show a ∼2.5‐m‐high scarp along the surface of a Quaternary drumlinoid ridge. Paleoseismic trenching and electrical resistivity tomography surveys across the scarp reveal a single reverse‐slip earthquake produced a fault‐propagation fold above a blind southwest‐dipping fault. Five geologically plausible chronological models of radiocarbon dated charcoal constrain the likely earthquake age to between 4.7 and 2.3 ka. Fault‐propagation fold modeling indicates ∼3.2 m of reverse slip on a blind, 50° southwest‐dipping fault can reproduce the observed deformation. Fault scaling relations suggest a M 6.1–7.6 earthquake with a 13 to 73‐km‐long surface rupture and 2.3–3.2 m of dip slip may be responsible for the deformation observed in the paleoseismic trench. An earthquake near this magnitude in Greater Victoria could result in major damage, and our results highlight the importance of augmenting instrumental monitoring networks with remote sensing and field studies to identify and characterize active faults in similarily challenging environments.
This study proposes a method of estimating the measurement data of nearby seismic stations by training an artificial neural network (ANN) through machine learning to understand the seismic acceleration time history at an arbitrary location where seismic acceleration time history is unknown. The ANN is trained using the observation data of 6 earthquakes at 10 ground seismic stations in Korea and 12 earthquakes at 212 underground seismic stations from the Korea Meteorological Administration. The location of the seismic station is assumed to be arbitrary in the untrained observation data to verify the validity of the trained ANN, and the measured and estimated data are compared. It is confirmed that the estimation accuracy of the ANN trained with the observation data of the underground seismic station is higher than that of the ANN trained with the observation data of the ground seismic station. The accuracy of the seismic acceleration estimation method proposed in this study is improved according to the level of learning data. It can also be applied as seismic acceleration to evaluate seismic damage or behavior of structures or facilities, even in places without seismic acceleration.
The world has faced serious landslide problems since the beginning of the twenty-first century when gigantic earthquakes occurred in Pakistan, China, and many other parts of the world. The damage was substantial not only because of the burial of houses under earth but also because of river blockage, the breaching of landslide dams, induced tsunami, compound effects with rainfall during the aftermath, and long-term slope instability. The susceptibility of slopes is affected by rock weathering, hydration, the dip of geological strata, antecedent rainfall, melting glacier, and many other processes in nature. It is thus reasonable to state that earthquake-induced landslides have to be investigated by those in numerous fields of science and technology such as engineering geology, geomorphology, rock/soil mechanics, sedimentology, geohydrology, and many others. Nevertheless, landslide experts have not undertook comprehensive study to date, although research and practice in their respective fields have achieved tremendously detailed developments. With this viewpoint, this report attempts to review a number of landslide studies in a variety of fields both in the past and in recent times, as well as the experience and knowledge gained from recent disasters. On the basis of those, a holistic and comprehensive perspective is presented. Certainly, the review of real disasters is the key to understanding the facts of landslides.
This document provides a detailed description of seismically-induced landslides and rockfalls that occurred in Italy during the 2016 Central Italy earthquake sequence. Relevant ground motion characteristics for all mainshocks of the sequence are analyzed. The document also provides a quantitative overview of spatial and temporal characteristics of the landslides and rockfalls that occurred during the earthquake sequence which was characterized by three mainshocks: (1) M6.1 on 24 August, (2) M5.9 on 26 October, and (3) M6.5 on 30 October. A relevant fraction of landslides has been caused by the first M6.1 mainshock; however, both the following events, especially the third M6.5 earthquake, exacerbated the slope instability in many locations and triggered several new and more serious ground failures. The overwhelming majority of the instabilities induced by the sequence are rockfalls in fractured rocks. Details of three selected case histories are described: (1) the Nera rockslide, (2) the Pescara del Tronto landslide, and (3) the Accumoli landslide. Rainfall data during 2016 are also shown and described for selected locations in the epicentral area.
Records of near‐fault ground motions from recent surface‐breaking earthquakes are characterized by large (> a few m/s), long‐period (a few seconds) ground velocity pulses, which may pose significant hazard for tall buildings and large infrastructures. Yet, the generation mechanism is not well understood. Here, using spontaneous rupture simulations, we examine the origin of large velocity pulses observed during the 2016 Mw7.0 Kumamoto (Japan) earthquake. We show that near‐fault waveform data as well as seismologically estimated moment and radiated energy can be well reproduced by a relatively simple model with uniform along‐strike pre‐stress and frictional properties. Our results suggest that large, long‐period ground velocities are caused by the dynamic interaction of propagating rupture and the Earth's surface, which is enhanced by reflected waves from the boundaries of low‐velocity layers. Such a generic mechanism suggests that large, long‐period ground motion is a common occurrence in near‐fault regions during surface‐breaking, strike‐slip earthquakes.
Precast segmental column bridges exhibit various construction advantages in comparison to traditional monolithic column bridges. However, the lack of cognitions on seismic behaviors has seriously restricted their applications and developments. In this paper, comprehensive investigations are conducted to analyze the dynamic characteristics of precast segmental column bridges under near-fault, forward-directivity ground motions. First, the finite-element models of two comparable bridges with precast segmental columns and monolithic columns are constructed by using OpenSees software, and the nonlinearities of the bridges are considered. Next, three different earthquake loadings are meticulously set up to handle engineering problems, namely recorded near- and far-field ground motions, parameterized pulses, and pulse and residual components extracted from real records. Finally, based on the models and earthquake sets, extensive explorations are carried out. The results show that near-fault forward-directivity ground motions are more threatening than far-field ones; precast segmental column bridges may suffer more pounding impacts than monolithic bridges; the “narrow band” effect caused by near-fault, forward-directivity ground motions may occur in bridges with shorter periods than pulse periods; and pulse and residual components play different roles in seismic responses.
We develop empirical estimates of site response at seismic stations in the Los Angeles area using recorded ground motions from 414 M 3–7.3 earthquakes in southern California. The data are from a combination of the Next Generation Attenuation-West2 project, the 2019 Ridgecrest earthquakes, and about 10,000 newly processed records. We estimate site response using an iterative mixed-effects residuals partitioning approach, accounting for azimuthal variations in anelastic attenuation and potential bias due to spatial clusters of colocated earthquakes. This process yields site response for peak ground acceleration, peak ground velocity, and pseudospectral acceleration relative to a 760 m/s shear-wave velocity (VS) reference condition. We employ regression kriging to generate a spatially continuous site response model, using the linear site and basin terms from Boore et al. (2014) as the background model, which depend on VS30 and depth to the 1 km/s VS isosurface. This is different from past approaches to nonergodic models, in which spatially varying coefficients are regressed. We validate the model using stations in the Community Seismic Network (CSN) that are in the middle of our model spatial domain but were not considered in model development, finding strong agreement between the interpolated model and CSN data for long periods. Our model could be implemented in regional seismic hazard analyses, which would lead to improvements especially at long return periods. Our site response model also has potential to improve both ground-motion accuracy and warning times for the U.S. Geological Survey ShakeAlert earthquake early warning (EEW) system. For a point-source EEW simulation of the 1994 M 6.7 Northridge earthquake, our model produces ground motions more consistent with the ground-truth ShakeMap and would alert areas with high population density such as downtown Los Angeles at lower estimated magnitudes (i.e., sooner) than an ergodic model for a modified Mercalli intensity 4.5 alerting threshold.
Child quadriceps muscle injuries are common in contact sports such as football and
basketball. The rectus femoris muscle component of the quadriceps muscle ıs frequently
ınjured, while vastus lateralis component of quadriceps muscle is rarely injured. In this case report, we aimed to draw attention to children's sports and the rare vastus lateralis muscle rupture. In this case, we detected the 13 years old football player with isolated vastus lateralis tendon rupture. After, We successfully treated this child with activity modification, physical therapy rehabilitation and exercises.
In our country, activities are carried out under the title of zoning studies in order to make an area suitable for
holistic living standards. There is a hierarchy in the formation of zoning plans from the upper scale of the country
development plans to the lower scale, which are the implementation zoning plans. With this hierarchy, in the
1/1000 zoning plans, social cultural areas are determined within the zoning boundaries determined to meet the
social activity needs of the people living in a region. Socio-cultural zoning islands can have different building
regulations, precedent or building heights. There are possible building regulations within the zoning boundaries,
where there may be different types of sitting areas, such as split, block and adjacent basis. The process of granting
construction permits to the existing zoning parcels in the zoning islands, whose identities are determined by these
building regulations, is the zoning scale. Zoning diameters, planned areas are given within the framework of type
zoning regulations and plan notes. The zoning diameter is given according to the precedent, height and building
order of the island. Distance method, on the other hand, is the process of creating the right residential area with
the drawing rules of convex shapes, such as square or rectangular, according to the geometric condition of the
parcel, in order to be able to give construction permits to the clean zoning parcels in the relevant zoning islands.
In our study, it has been tried to show how the settlement areas on the floor can be given, which building order,
which precedent and how to apply the process to the convex parcels with the distance approach.
Shaking table test is an important means for the seismic research of structures, and many scholars have conducted shaking table tests on bridge structures. However, relatively few studies have focused on a curved bridge with a longitudinal slope. In this research, a 1/10-scale test model of a curved bridge with the different pier hights was designed by the principle of structural test similarity. The seismic records in the hanging-wall (HW), footwall (FW), and neutral zones were selected to conducted shaking table tests. Results showed that the seismic spectrum and peak value are remarkably affected by HW ground motions and have strong destructive power. The dynamic response of the curved bridge is remarkable under HW seismic records. The motion form of main girder is spatial and produces obvious rotation under HW seismic records. The displacement response of the curved bridge is closely related to the height of piers and the angle between pier displacement and seismic input directions. The displacement responses at the beam end and the bearing displacement are related to the motion state of the main girder.
The distribution of ground motion, displacement, and secondary hazards around active faults is defined by the interaction of tectonic and site characteristics including fault kinematics. As a result of this complexity, recommendations for fault setback distances or avoidance zones are necessarily simplified. We observed distributed vertical coseismic displacement from the 2016 Mw 7.8 Kaikōura earthquake up to c. 500 m on either side of the sinistral-reverse Papatea fault. On average, c. 32% (2.13 m) of vertical displacement was measured at distances >50 m from the Papatea fault. Additionally, in places, there is strong asymmetry where displacement was accommodated over a wider area in the hanging wall of the fault, a common observation around many dip-slip fault ruptures globally. We compare the distribution of displacement around the Papatea fault to the current fault avoidance zone and find that increasing the size of the fault avoidance zone by 10 m captures 11% more area with a high gradient of vertical displacement. Given these results and similar findings for other faults globally, we recommend that existing standards for fault avoidance zones be evaluated to ensure their ongoing efficacy.
We present a modeling technique for generating synthetic ground motions, aimed at earthquakes of design significance for critical structures and ground motions at distances corresponding to the engineering near field, in which real data are often missing. We use dynamic modeling based on the finite-difference approach to simulate the rupture process within a fault, followed by kinematic modeling to generate the ground motions. The earthquake source ruptures were modeled using the 3D distinct element code (Itasca, 2013). We then used the complete synthetic program by Spudich and Xu (2002) to simulate the propagation of seismic waves and to obtain synthetic ground motions. In this work, we demonstrate the method covering the frequency ranges of engineering interests up to 25 Hz and quantify the differences in ground motion generated. We compare the synthetic ground motions for distances up to 30 km with a ground-motion prediction equation, which synthesizes the expected ground motion and its randomness based on observations. The synthetic ground motions can be used to supplement observations in the near field for seismic hazard analysis. We demonstrate the hybrid approach to one critical site in the Fennoscandian Shield, northern Europe.
Given its location in a convergence zone of the African and Eurasian plates, northern Algeria is seismically active, this is due to the presence of several seismogenic faults, whose exact trace is often unknown. The study of the fault damage zones plays an important role in seismic hazard assessment and microzonation studies, as well as in the site effects analysis, and is also used to determine the exact location of the faults.
The objective of this thesis is to characterize the fault damage zones that border the Mitidja, through the study and the site effects analysis by the ambient noise H/V technique. First, the H/V was used to determine the resonance frequencies of the soil, and to classify the frequency curves but also to make the iso-frequency map and finally to estimate the thickness of the geological formations allowing the evaluation of the amplification. Moreover, and thanks to this method, we were able to map the roof of the metamorphic basement and follow its spatial evolution at more than 230 m deep.
Secondly, the research was oriented on the applicability of the H/V technique in the location of active faults. The HVSR method was sometimes combined with electrical tomography. This approach was carried out on the Thénia fault, the Sahel fault and the South Mitidjian fault, while attempting to highlight the signature of the fault zone on the spectral responses. The correlation between the two techniques, allowed to image the subsurface structure of the fault damage zone.
A second approach based on the analysis of directional amplification was experimented and has proven to be very useful in the characterization and localization of complex geological zones.
The 1994 Northridge Earthquake is selected as an example to discuss the ability of three pulse-like ground motion identification methods. Wavelet analysis, peak-point method (PPM) and zero velocity point method (ZVPM) are used. Pulse indictor (PI) is calculated to identify pulse-like ground motions from 314 near-fault records. Peak ground velocity (PGV) and pulse period (Tp ) of the pulse-like motion from these three methods are compared. Most of the pulse periods from PPM are smaller than those from the other two methods. And, most stations with pulse-like ground motions are located on the hanging wall. The effect of velocity pulse on response spectra is investigated further. The amplification at the hanging wall stations is more serious than that at the footwall stations.
This article scrutinizes the determination of input motions for forensic ground-response analysis in the near-source region, based on recorded surface ground motions at strong-motion station sites, from the same event. The first part of the article draws upon observed ground motions from the 22 February 2011 6.2 M w Christchurch earthquake to discuss key challenges of the problem associated with the strong spatial variation of ground motion in the near-source region. Effects from the complexity of the rupture, propagation of seismic waves through complex geological structures, and site characteristics are explored. It is argued that, because of the strongly varying source-path “signature” on near-source ground motions, “reference” input motions for ground-response analysis must be specific to, and have similar signature characteristics (be “compatible”) with, the target site which is subject to the analysis. The second part of the article presents a four-step procedure for the derivation of site-specific input motions involving (1) determination of the reference layer where the input motion is to be applied in the analysis, (2) record selection considering the appropriateness of the recording station site for deconvolution and its compatibility with the target site, (3) deconvolution of the selected record to remove local site effects from the recorded ground motion, and (4) scaling of the deconvolved motion to account for differences in the source-to-site distance between the recording station and the target site. As part of the proposed procedure, a novel (amplitude-duration) scaling method is presented. Results from one-dimensional (1D) effective-stress analysis of two target Christchurch sites using input motions from the proposed procedure are used to critically evaluate the procedure and discuss essential requirements for its successful application.
Permanent displacement of a bridge column can be directly measured during the inspection after near-fault earthquakes. However, the engineer needs to estimate the expected residual drift at the design stage to determine if the bridge seismic performance is satisfactory. The most direct method to estimate the residual displacement is nonlinear response history analysis, which is time consuming and cumbersome. Alternatively, an attractive but indirect method is generating estimated residual displacement spectra that depend on displacement ductility demand, column period, site conditions, and earthquake characteristics. Given the period and the expected displacement ductility demand for the column, the residual drift response spectra curves can be utilized to estimate the residual drift demand. Residual drift spectra that are applicable to RC bridge columns in different parts of the United States were developed based on nonlinear response history analyses using a comprehensive collection of recorded and synthetic near-fault ground motions and were linked to one-second spectral acceleration (S1) of the AASHTO maps. It was also found that the residual drift ratio is below one percent when S1 is less than 0.6 g.
Thrust-fault earthquakes are particularly hazardous in that they produce stronger ground motion than normal or strike-slip events of the same magnitude due to a combination of hanging-wall effects, vertical asymmetry, and higher stress drop due to compression. In addition, vertical surface displacement occurs in both blind-thrust and emergent thrust ruptures, and can potentially damage lifelines and infrastructure. Our 3D dynamic rupture modeling parameter study focuses on planar thrust faults of varying dip angles, and burial depth establishes a physics-based understanding of how ground motion and permanent ground surface displacement depend on these geometrical parameters. We vary dip angles from 20° to 70° and burial depths from 0 to 5 km. We conduct rupture models on these geometries embedded in a homogeneous half-space, using different stress drops but fixed frictional parameters, and with homogeneous initial stresses versus stresses tapered toward the ground surface. Ground motions decrease as we bury the fault under homogeneous initial stresses. In contrast, under tapered initial stresses, ground motions increase in blind-thrust faults as we bury the fault, but are still the highest in emergent faults. As we steepen dip angle, peak particle velocities in the homogeneous stress case generally increase in emergent faults but decrease in blind-thrust faults. Meanwhile, ground motion consistently increases with steepening dip angle under the stress gradient. We find that varying stress drop has a considerable scalar effect on both ground motion and permanent surface displacement, whereas changing fault strength has a negligible effect. Because of the simple geometry of a planar fault, our results can be applied to understanding basic behavior of specific real-world thrust faults.
As the forward directivity and fling effect characteristics of the near-fault ground motions, seismic response of structures in the near field of a rupturing fault can be significantly different from those observed in the far field. The unique characteristics of the near-fault ground motions can cause considerable damage during an earthquake. This chapter presents results of a study aimed at evaluating the near-fault and far-fault ground motion effects on nonlinear dynamic response and seismic damage of concrete gravity dams including dam-reservoir-foundation interaction. Nonlinear dynamic response and seismic damage analyses of concrete gravity dams subjected to both near-fault and far-fault ground motions are performed. The results obtained from the analyses of the dam subjected to each fault effect are compared with each other.
Landslides represent the most frequent geological hazard in mountainous environments. Most notably, landslides are a major source of fatalities and damage related to strong earthquakes. The main aim of this research is to show through three-dimensional engineer-friendly computer drawings, different mountain environments where coseismic landslides could be generated during shallow crustal and megathrust earthquakes in the Andes of central Chile. We have determined topographic, geomorphological, geological and seismic controlling factors in the occurrence of earthquake-triggered landslides from: (1) a comparison of local earthquake-induced landslide inventories in Chile (the M w 6.2, shallow crustal Aysén earthquake in 2007 (45.3° S) and the M w 8.8, megathrust Maule earthquake in 2010 (32.5°S–38.5°S)) with others from abroad; and (2) analysis of large, prehistoric landslide inventories proposed as likely induced by seismic activity. With these results, we have built four representative geomodels of coseismic landslide geomorphological environments in the Andes of central Chile. Each one represents the possible landslide types that could be generated by a shallow crustal earthquake v. those likely to be generated by a megathrust earthquake. Additionally, the associated hazards and suggested mitigation measures are expressed in each scenario. These geomodels are a powerful tool for earthquake-induced landslide hazard assessment.
Thematic collection: This article is part of the Ground models in engineering geology and hydrogeology collection available at: https://www.lyellcollection.org/cc/Ground-models-in-engineering-geology-and-hydrogeology
A preliminary rupture model of the 1994 Northridge, California earthquake, determined
from strong motion waveform inversion and analysis, is presented. The fault rupture plane
chosen is based on the distributions of aftershocks and teleseismic surface-wave and bodywave
point-source solutions. The fault strikes 122°, dips 42°, and has a slip vector of 109°.
The average slip is about 1.2 meters over the rupture area and the peak slip reaches nearly
4 meters. Our estimate of the seismic moment is 1.2 ± 0.2 x 10^(26) dyne-cm. The area of
rupture is small relative to the aftershock dimensions and is approximately 14 km along
strike (west-northwest from the hypocenter) and nearly 20 km in the updip direction. There
is little indication of slip shallower than about 7 km.
The up-dip, near-source strong-motion velocity waveforms show two distinct, large S-wave
arrivals 2-3 sec apart (as do the teleseismic P waves), indicating separate source subevents.
An along strike (west-northwest) subevent separation of about 8 km is most consistent with
the observation that the two main arrivals are separated more in time to the south and
southeast (about 4.5 sec at Stone Canyon Reservoir and Sherman Oaks, for example), than
at northern azimuths. The interpretation of secondary arrivals observed at more distant
stations to the south and southeast (e.g., Santa Monica) is more tenuous, since several of
the aftershocks recorded there indicate later arrivals as well. However, a secondary source
contribution is expected based on our model of the closer stations.
After placing these constraints on the general nature of the rupture, we predict the characteristics
of the long-period (1-10 sec) ground velocities over a grid of stations covering the
near-source region. This exercise provides a basis for separating the effects of source radiation
(dominated by radiation pattern and directivity) from the complex waveform modifications
due to wave-propagation and site response.
The peak accelerations recorded on alluvial sites during the Northridge earthquake were about 50% larger than the median value predicted by current em-pirical attenuation relations at distances less than about 30 km. This raises the ques-tion of whether the ground motions from the Northridge earthquake are anomalous for thrust events or are representative of ground motions expected in future thrust earthquakes. Since the empirical data base contains few strong-motion records close to large-thrust earthquakes, it is difficult to assess whether the Northridge ground motions are anomalous based on recorded data alone. For this reason, we have used a broadband strong-motion simulation procedure to help assess whether the ground motions were anomalous. The simulation procedure has been validated against a large body of strong-motion data from California earthquakes, and so we expect it to produce accurate estimates of ground motions for any given rupture scenario, in-cluding blind-thrust events for which no good precedent existed in the strong-motion data base until the occurrence of the Northridge earthquake. The ground motions from the Northridge earthquake and our simulations of these ground motions have a similar pattern of departure from empirical attenuation relations for thrust earth-quakes: the peak accelerations are at about the 84th percentile level for distances within 20 to 30 km and follow the median level for larger distances. This same pattern of departure from empirical attenuation relations was obtained in our simu-lations of the peak accelerations of an Elysian Park blind-thrust event prior to the occurrence of the Northridge earthquake. Since we are able to model this pattern with broadband simulations, and had done so before the Northridge earthquake oc-curred, this suggests that the Northridge strong-motion records are not anomalous and are representative of ground motions close to thrust faults. Accordingly, it seems appropriate to include these recordings in strong-motion data sets that are used to develop empirical ground-motion attenuation relations for thrust faults and to use this augmented data set as the basis for evaluating the need for modifications in design coefficients in the seismic provisions of building codes.
This report presents a numerical method for computing response spectra from strong-motion earthquake records. The method is based on the exact solution to the governing differential equation and gives a three to four-fold saving in computing time compared to a third order Runge-Kutta method of comparable accuracy. An analysis was made of the errors introduced at various stages in the calculation of spectra so that allowable errors could be prescribed for the numerical integration. Using the proposed method of computing or other methods of comparable accuracy, example calculations show that the errors introduced by the numerical procedures are much less than the errors inherent in the digitization of the acceleration record.
Included as appendices to the report are computer programs in Fortran IV, with instructions for their use, for computing spectra, for correction of the baseline of the digitized record, and for the computation of ground velocity and displacement.
Estimation of hanging wall and foot wall effects on peak acceleration
- Abrahamson
Abrahamson, N. A. and P. G. Somerville (1993). Estimation of hanging
wall and foot wall effects on peak acceleration, Proc. International
Workshop on Strong Motion Data, Menlo Park, California, Vol. II,
351-360.
Personal communication referenced by
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Sadigh, K. (1987). Personal communication referenced by Joyner and
Boore (1988), Ground Motion Prediction, Proc. ASCE, Earth. Eng.
Soil Dyn., 11, Recent Advance in Ground Motion Evaluation, p. 67.
Federal Services 566 E1 Dorado Street Pasadena
- Woodward-Clyde
Woodward-Clyde Federal Services
566 E1 Dorado Street
Pasadena, CA 91101
(P.G.S.)
Manuscript received 27 January 1995.
Updated coefficients for ground motion estimates including differences between strike- and reverse-slip faults
- D M Boore
- W Joyner
- T Fumal
Boore, D. M., W. Joyner, and T. Fnmal (1994). Updated coefficients for
ground motion estimates including differences between strike-and
reverse-slip faults, personal communication to SCEC, April 1994.
Empirical prediction of near-source ground motion from large earthquakes
- Campbell
Campbell, K. W. (1993). Empirical prediction of near-source ground motion from large earthquakes, Proc. International Workshop on Earthquake Hazard and Large Dams in the Himalaya, January 15-16,
1993, New Delhi, India.
Selection of earthquake ground motions at rock sites
- Idriss