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Earthquakes along the Dead Sea Transform (DST) and in the Dead Sea Basin pose a considerable seismic hazard to the city of Jerusalem. To assess possible local site amplification due to either stratigraphical or morphological effects, we conducted seismic noise measurements at the Basilica of the Holy Sepulchre.The fact that the Basilica is built partially on detrital covers and alluvial filling provides further motivation for the study. Noise data are complemented by two earthquakes that were recorded at three seismic stations during the field measurement period.The results do not indicate site amplification at the Basilica ground, at least not for the major eigenfrequencies of the building.
... With a growing interest in the protection of historical monuments, the usage of a quick and non-invasive microtremor HVSR methodology with no environmental impacts started to become more and more popular (e.g. Del Monaco et al. 2013;Ditommaso et al. 2010;Fäcke et al. 2006;Fiaschi et al. 2012;Gentile and Saisi 2007;Moisidi et al. 2004;Nakamura et al. 1999Nakamura et al. , 2000Stanko et al. 2016). It is the easiest and cheapest way to understand structural behaviour without doing any harm to a structure. ...
... The application of a microtremor HVSR methodology has been used to determine the natural frequency of historical monuments (e.g. Del Monaco et al. 2013;Ditommaso et al. 2010;Fäcke et al. 2006;Fiaschi et al. 2012;Gentile and Saisi Environ Earth Sci (2017) 2007; Moisidi et al. 2004;Nakamura et al. 1999, Stanko et al. 2016. Microtremor ambient noise measurements have been taken to detect potential weak points in the structure of Trakošćan Castle, primarily the construction of the Castle Tower due to earthquake damage and improper reconstruction (Stanko et al. 2016). ...
This paper presents a major extension of seismic vulnerability research project on the site of Trakošćan Castle based on the initial horizontal-to-vertical-spectral-ratio (HVSR) results from Stanko et al. (2016). The estimated HVSR site frequencies and HV amplification at Trakošćan Castle can only be used as an indication of the initial soil site frequency and amplification, so-called natural soil model, corresponding to the subsoil profile without the influence of an earthquake. The equivalent-linear (EQL) site response analysis has been carried out for different earthquake scenarios for a maximum input rock peak ground acceleration (PGAROCK) that corresponds to return periods of 95 (0.08 g), 475 (0.18 g) and 1000 years (0.31 g). The aim of the research is to evaluate structural seismic design responses and to determine type and degree of damage caused by local site effect, which is the result of an alluvial basin and topographic influences. The main objective of this research is the formation of local microseismic zones based on an EQL analysis: surface spectral acceleration and amplification maps at the predominant frequency. Based on the HVSR frequency response of the core structure of Trakošćan Castle and the Tower itself (fundamental and higher frequency modes), maps of surface spectral acceleration and soil amplification at different frequencies (3, 5 and 10 Hz) are developed for different input PGAROCK levels (0.08, 0.18 and 0.31 g) to evaluate seismic response of the Castle. Observed amplifications are correlated with ground motion polarization and directionality of the ground motion from the alluvial basin to the hilltop. Shortening of predominant frequencies (lengthening of the period), particularly in the alluvial basin, has been observed with higher input PGAROCK in the EQL analysis. This effect is not manifested in the Trakošćan hill, and predominant frequencies match HVSR frequencies. The use of certain geophysical survey methods at historical sites is a big problem, because terrain features (e.g. steep hills, mountains, ridges, slopes, cliffs) create lack of space and make it impossible to carry out geophysical investigation. Microtremor measurements at historical sites can overcome this limitation and provide local seismic response and vulnerability behaviour of historical monuments without destroying their authenticity. Also, computational modelling can greatly improve the results. The EQL site response analysis on the site of Trakošćan Castle has confirmed and improved the results of seismic response and vulnerability based on HVSR method.
... Therefore, the main aim of this study is two-fold: (a) the assessment of earthquake damage in the Castle after the earthquakes that occurred in 2020, and (b) the comparison of pre-(2016) and post-earthquake (2021) ambient vibration measurements of critical points. Pre-and post-earthquake ambient vibration measurements in historical buildings can help to identify potential hidden cracks in thick walls and to detect potential weak points in the complex structure [9,10]. Changes in the fundamental frequencies can provide a useful tool for vulnerability diagnosis [11,12]. ...
Trakošćan Castle, built on a rocky peak in the late 13th century, is a cultural heritage site protected as a historical entity by the Republic of Croatia. The Castle is constructed as a highly irregular masonry structure with timber or shallow masonry arches, vaults or dome floors. It was substantially renewed, upgraded and partially retrofitted from the 16th century until the year 2000. The M5.5 (VIII EMS) and M6.2 (VIII-IX EMS) earthquakes, which struck the city of Zagreb on 22 March 2020 and the Pokupsko-Petrinja area on 29 December 2020, strongly shook the Castle’s structure. Earthquake damage was observed and assessed by visual inspection accompanied by ambient vibration measurements. The slight cracks that appeared on masonry arches were found to be critically positioned, and can likely lead to the arches’ collapse if their spreading is not prevented. Ambient vibration measurements, which were compared to pre-earthquake ones, revealed the decrease in the fundamental frequencies of the Castle’s central tower unit and the second floor, thus possibly indicating the loss of structural stiffness as a consequence of the earthquake damage.
... In fact, these methods are normally employed both to test the conservation status of buildings/structures as their natural frequencies, and to assess damping and modal shapes, that are directly related to the structural rigidity and integrity. The bibliography about buildings/structures seismic risk/vulnerability assessment, as well as their seismic dynamic characterization, is wide (Stewart and Fenves 1998; Ramos et al. 2010, Fiaschi et al. 2012, Barbieri et al. 2013 Casolo et al. 2013; Russo 2013; Asteris et al. 2014; Ceravolo et al. 2014; Aguilar et al. 2015; Lacanna et al. 2016 and references within, and Pazzi et al. 2016a, b). On the other hand, papers about the seismic response of structures/buildings during conservation/safety works are missing, even thought the seismic vibration monitoring (SVM) is a technique widely used during these kind of works. ...
The concepts of disaster risk reduction and disaster risk management involve the development, improvement, and application of policies, strategies, and practices to minimize disaster risks throughout society. Nowadays, preserving architectural heritage and ancient monuments from disasters is an important issue in the cultural life of modern societies. The “health” of a building/structure may be evaluate by its deterioration or damage level: monitor the aging and promptly detect relevant damages, play a central role, and structure dynamic characterization and microtremor analysis are considered powerful techniques in this field. A wide bibliography about structures/buildings seismic dynamic characterization is counterpoised to a missing one about their seismic response during conservation/safety works. This paper focus on the seismic response and monitoring of a historical masonry embankment wall during the conservation works carried out after a riverbank landslide that seriously damaged it. ResultsThe H/V results of the acquired traces show that main resonance frequency of the masonry embankment wall is between 4 Hz and 15 Hz, in agreement with the frequency range of roughly 10-meters-high, squat and monolithic structure. The whole monitoring period can be divided into three intervals corresponding to three different kind of workings: i) piling work; ii) parapet breakdown, excavation, embankment arrangement and foot wall consolidation; iii) backfill and restoring of the original condition, ordinary construction activities. The maximum peak component particle velocity substantial increase during the second period. All the stations have a higher energy content in the 10-20 Hz frequency range, but the spectra analysis clearly shows that the NS component, perpendicular to the wall, is the most stressed one. Moreover, despite the considerable distance from the August 24 Central Italy earthquake epicentre, the earthquake waveform is clearly recognizable at each station. In fact, the energy is focused around 2 Hz and the signals show directivity neither for the spectrum nor for the H/V. Conclusion
This work may contribute to characterize the vibrations induced by piling work at close range, and help to define the maximum acceptable vibration pattern for such structures, since literature is missing of such case studies. The maximum peak component particle velocity values clearly showed the work advancement. This paper also shows how the H/V technique is a valuable method to estimate the resonant frequency not only of buildings, but also of a squat and monolithic structure like the Lungarno Torrigiani masonry embankment wall.
... Microtremor measurements in buildings and structures were used to assess the dynamic structural characteristics, fundamental frequencies of structures, and the possible soil-structure interaction/resonance (e.g., Gallipoli et al. 2010;Gosar 2012;Herak 2011). With the growing interest to protect historical monuments, the application of the quick and noninvasive microtremor HVSR methodology with no environmental impacts started to become more and more used (e.g., Fäcke et al. 2006;Fiaschi et al. 2012;Gentile and Saisi 2007;Moisidi et al. 2004;Nakamura et al. 1999Nakamura et al. , 2000. ...
The Trakošćan Castle was built on the rocky peak of the hill in the thirteenth century. Castle structure has weakened with time, wars, inappropriate protection, and earthquakes. On 16 March 1982, the Tower Castle and part of second floor were damaged by an earthquake (ML= 4.5) with an epicenter 20 km distance from Mt. Ivančica. Afterwards, it was completely reconstructed. Today the cultural heritage of the Trakošćan Castle is protected as a historical entity by the Republic of Croatia. The Horizontal-to-Vertical-Spectral-Ratio (HVSR) method was applied for the purpose of local seismic response, protection from earthquake, structural seismic vulnerability of weak points, and structural restoration of the Trakošćan Castle related to the 1982 earthquake (microtremor measurements in free-field and in the Tower Castle). The free-field HVSR results (soil fundamental frequencies, amplification factors, shear wave velocity distribution, estimated bedrock depth, and directional effects on ground motion) are compared to the local geology, propagation path, and topographic effects to the estimated local seismic response. The dynamic behavior of the Tower Castle is demonstrated along different axes by the comparison of the directional HVSR analysis to the horizontal components (NS/V and EW/V) and the amplitude spectra (NS, EW and UD). The modal frequency response identifies weak points of the Tower Castle structure. Based on the HVSR analysis, the damage at Trakošćan site, related to the 1982 earthquake, occurred due to the local geology and topographic effects (seismic energy directed through the alluvial basin and trapped into the hill) and the improper way of the Tower Castle construction in the past and the reconstruction after the earthquake.
... The methodical study of seismic safeguard of artistic heritage has considerably spread in the last years, thus increasing researchers' interest in problems concerning monumental buildings. In particular, the seismic safety of art objects, that are the objects generally contained within Museums, is a research field of great interest, being part of research and policy in the more general field of Cultural Heritage, with contribution of several local government and European research grants (Liberatore 2000;Fiaschi et al. 2012). It must be noted, in fact, that buildings of historical and cultural significance may contain objects of inestimable value, for which there is no assessment of their effective vulnerability related to how they are displayed or stored. ...
The problem of reducing the seismic risk for art objects, that are the objects generally contained within Museums, is of great interest. The first studies were performed in Japan and were successively organized in a general framework by a research program performed at Southern California University and sponsored by the Getty Museum at Malibu, California. In these papers and in the following Italian studies, the theoretical models for the problem concerning vases and statues are based on the dynamic behavior of rigid blocks and have been deeply developed. Unfortunately, because of the great lack of experimental data, determinant parameters for the problem characterization (like the friction between two superimposed blocks or between the art object and the support plane) are often assumed without reference to real values derived from laboratory tests. This paper presents the results of a research program containing the experimental determination of the friction coefficient between the art object and the support (by means of a testing apparatus on purpose realized) together with dynamic tests performed on simple-shaped objects made of different materials. The dynamic tests were performed using an unidirectional shaking table and different supporting surfaces, so that the influence of different friction coefficients has been analyzed.
Palazzo della Ragione, erected in 1233, represents one of the most ancient and relevant historic building of Milan. During the last century, the Palace suffered significant modifications, including the realization of an underground tunnel immediately near the foundations. Numerical analysis conducted with a FEM model were developed on the basis of some experimental tests. In particular, the diagnostic campaign performed in 1979, in which flat jacks and dynamic tests were applied, allowed to obtain useful information on the mechanical characterization of the masonry. In addition, the execution of some dynamic identification tests in 2017 returned the own frequencies of the building 40 years later. Before to work on the structural project, the autor verified the consistency between the structural response of the numerical model and the one of the real building, obtained by dynamic tests. Some consolidation interventions were realized on the wooden trusses of the cover, in order to restore either local and global safety situation, with respect to vertical and horizontal load.
Instrumental estimates of transfer functions have been performed at selected localities in the archaeological site of Ancient Aptera, Crete Island, Greece, in order to examine the occurrence of site effects and identify the dynamic characteristics of the archaeological finds. Final objective is the evaluation of the risk of structure damage or collapse in case of future events using microtremor recordings (i.e. low-amplitude oscillations of ground surface produced by natural sources or by anthropogenic noise). It is worthwhile to notice that there hasn't been conducted any previous seismic study in the area. This work includes measurement, analysis and interpretation of ambient noise data as well as application of electrical tomography method. Registrations have been performed by means of a tridirectional sensor Lennartz 3D-Lite (1 Hz frequency), connected with a 24-bit digital acquisition unit. A set of 10 time series of 800 second each, sampled at 125 Hz, was recorded in several sites. The selected stationary time windows of each time series were corrected for the base line and for anomalous trends, tapered with a cosine function to the first and last 5% of the signal, and band pass filtered from 0.5 to 20 Hz with cut off frequencies at 0.3 and 22 Hz. The same procedure was performed for all sites and components and finally the H/V spectra were computed. Most of the sites present significant amplification peaks in frequency between 2 to 3 Hz. Finally, electrical resistivity tomography was carried out. The extracted results clearly show a very complex subsurface geometry indicated by the presence of large scale voids, which may possibly correspond to ancient reservoirs. We confirm that the selected site of cultural heritage consists of a very complex subsurface structure and that the results obtained by HVSR method and by geophysical method are very well correlated.
An application is presented of a recently proposed system identification method for buildings that takes into account the effects of soil-structure interaction and the coupling of the horizontal and rocking motions of the foundation. The method gives the uncoupled structural fixed-base frequency f1 and rigid-body rocking fre- quency fR using data only from two horizontal sensors (at base and roof). The fixed-base frequency is estimated from the wave travel time through the structure, the apparent system frequency from Fourier analysis, and the rocking frequency from a relation between these three. The case study is Millikan Library in Pasadena, Cali- fornia. Results are shown for four earthquakes between 1970 and 2002. The method makes it possible to quantify the degree to which the observed changes (wandering) of its resonant frequencies have been due to changes in the structure alone. The results show that (1) both f1 and fR are amplitude dependent, (2) significant permanent re- duction of frequency occurred over the years, ∼22% for f1 and 11% for the apparent frequency f1;app, mostly caused by the San Fernando earthquake of 1971, while (3) the changes of fR have been amplitude dependent and recoverable. (4) During the San Fernando earthquake, both f1 and fR dropped, respectively, by ∼24% and ∼18%, resulting in 21% drop of f1;app. (5) After this earthquake, the changes in the observed resonant frequencies, which are those of the system, have been due to a much larger degree (4-5 times) to changes of fR than to changes of f1. (6) The small permanent changes in f1 that appear to have occurred after the San Fernando earthquake cannot be deciphered with certainty because of the small number of earthquake records avail- able for this analysis since 1971. Records from the period 1988 to 2002, when re- leased, can be used in future to refine and verify these trends.
Jerusalem was hit by earthquakes several times in its history, in the course of which none of the holy sites of the three
main faiths of the western world escaped damage. Intensities of the last ML 6.2, July 11, 1927 Dead Sea earthquake, reached MSK VIII in the Old City of Jerusalem and the surrounding villages. As future
strong earthquakes are inevitable, the need for the evaluation of earthquake-related hazards is obvious. Only general geotechnical
properties of the section exposed in the mountainous area of Jerusalem are available; therefore, the hazard assessment was
conducted from a geological perspective. The hazards identified in this study are: (1) amplification of seismic acceleration
due to soft rock and soil conditions; (2) amplification due to mountainous topography; (3) dynamic instability of natural
slopes; and (4) potential failure of slopes that have undergone engineering development and were weakened due to damaging,
steepening, overloading, and wetting beyond their natural state. We formulated relative grades of vulnerability for each of
the hazards and delineated the zones that require further specific investigation. For practical use we constructed a summary
map that combines the different hazard categories. Looking at the summary map, the ground at the central N–S axis zone across
Jerusalem is the least vulnerable. The bedrock there is mostly hard carbonate, the topography is mild, and thus only the alluvial
cover, if thicker than 3m, should be considered sensitive. Yet although the natural hazard in this area is limited, the risk
should not be underrated. Much of the city lies there, including buildings constructed before antiseismic codes were regulated,
and traditional engineering practice should not be taken for granted as antiseismic proof either. Eastwards, the shear wave
velocity (Vs) contrast between the hard and soft rocks as well as the notable topography in places, impose the potential for
amplification. Slopes, either naturally or artificially cutting into the soft chalk, may expose the area to dynamic instability;
thus, the ongoing extensive development of the city in this direction should certainly take into account all of this. West
of the central axis, the potential of failure of both steep natural and urbanized slopes appears. Being a plausible direction
for future urban expansion, these areas specifically call for careful environmental and engineering planning. For engineering
purposes, however, a specific site investigation is still necessary. Nevertheless, the summary map established in this study
sets up for Jerusalem, for the first time, a practical tool for environmental and municipal planning, emergency response planning,
and civil protection.
KeywordsJerusalem-Earthquake-related hazards-Ground amplification-Topographic amplification-Slope stability
Ambient seismic noise measurements were conducted inside the Cathedral of Cologne (Germany) for assessing its frequencies
of vibration and for checking whether these occur in the range where soil amplification is expected. If this is the case,
damages may increase in case of an earthquake due to an increased structural response of the building. Analysis of the ratio
between the horizontal and vertical components of the spectra recorded at stations located inside the building as well as
the ratio between the corresponding components of the spectra recorded simultaneously inside the building and at a reference
station placed in the basement of the cathedral indicated several modes of vibration. Facilitated by these results an assessment
of the seismic vulnerability was attempted for a 2D ground motion scenario using the finite element method.
The aim of this paper is to discuss the existing scientific literature in order to gather all the available information dealing with the origin and the nature of the ambient seismic noise wavefield. This issue is essential as the use of seismic noise is more and more popular for seismic hazard purposes with a growing number of processing techniques based on the assumption that the noise wavefield is predominantly consisting of fundamental mode Rayleigh waves. This survey reveals an overall agreement about the origin of seismic noise and its frequency dependence. At frequencies higher than 1 Hz, seismic noise systematically exhibits daily and weekly variations linked to human activities, whereas at lower frequencies (between 0.005 and 0.3 Hz) the variation of seismic noise is correlated to natural activities (oceanic, meteorological…). Such a surface origin clearly supports the interpretation of seismic noise wavefield consisting primarily of surface waves. However, the further, very common (though hidden) assumption according which almost all the noise energy would be carried by fundamental mode Rayleigh waves is not supported by the few available data: no “average” number can though be given concerning the actual proportion between surface and body waves, Love and Rayleigh waves (horizontal components), fundamental and higher modes (vertical components), since the few available investigations report a significant variability, which might be related with site conditions and noise source properties.
This article addresses several issues relevant to a better understanding of why archaeologists have generally failed to reach a consensus on the dating, regional impact, or identification of earthquake destructions in the depositional records of Roman / Byzantine Palestine and the province of Arabia. An evaluation of earthquake destructions in these regions from the 2nd through the mid-8th century A. D. is based upon an analysis of both ancient textual accounts and contemporaneous archaeological data. Depositional processes affecting archaeoseismic destruction evidence as it appears in the archaeological record are also discussed.
It is well known that artificially inducing large amplitude vibrations on buildings produces seismic waves that are detectable up to a few kilometers away. Does a similar effect occur with seismic tremors? If the tremor wave field were perturbed by the presence of buildings, passive surveys in a urban environment would be potentially impaired. The literature is rather inconclusive on this issue. We experimentally analyzed the cases of three of the most famous Italian towers: the leaning tower of Pisa, the bell tower of San Marco in Venice, and the Asinelli tower in Bologna. We also analyzed a large modern 16 story residential building. Even performing the measurements in windy days, we found no cases in which the large structures perturb the free-field tremor at distances larger than 12 m. This confirms what was expected from simple dimensional analysis and suggests that passive soil-structure interaction is of little concern for standard buildings and standard ambient conditions.
A study of major earthquake occurrence along the Dead Sea transform (35.5°–36.5° E; 27.2°–37.5° N) during the past four millenia has been attempted. Geological, archaeological, biblical, historical, and seismological evidence were integrated in an effort to quantify the space-time distribution of seismicity in the said province. The overall earthquake activity in the conterminous Near East indicates a stable pattern and appeared to have been stationary over the examined time window. About 110 earthquakes in the magnitude range 6.7 ≤ ML ≤ 8.3 affected the area during the past 2500 years. Of these, 42 originated along the Dead Sea fault system itself, while 68 were imported from the Helenic-Cyprian arcs and the Anatolian-Elburz-Zagros fault systems. These events were responsible for the repeated destruction of many cultural centers. In the Dead Sea region proper, the major seismic activity since 2100 B.C.E. (Before Christian Era), has been confined to the vicinity of its eastern shore with extremal seismicity at its southern tip near the prehistorical site of Bab-a-Dara'a (31° 15'N, 35° 32'E). This may constitute the first solid evidence that the Biblical “cities of the Plain” (Sodom, Gommorah, etc.) were located there. Recent studies of earthquake deformations in the Lisan deposits near Bab-a-Dara'a, agree with our findings. At the present time, a magnitude 6¾ earthquake is pending at the northern edge of the Levant rift, with its average recurrence interval (83 years) exceeded by one standard deviation (32 years).
As methods for dynamic characteristics estimation of surface layers, investigation of boreholes and a method which employs microtremors are well known. Borehole investigation, one of the most accurate methods, is costly and time-consuming and is not available all the time. The method that employs microtremors is handy but has not produced satisfactory results to this day. This paper describes a new processing method that employs microtremor observations yet produces accurate estimates of the characteristics of the ground motion. The method uses a vertical component and horizontal components. As a result, the spectrum ratio of the horizontal components and the vertical component of the microtremors bears a resemblance to the transfer function for the horizontal motion of the surface layers.
The motion of a building depends on the excitation, the coupling of the building to the ground, and the mechanical properties of the building. We separate the building response from the excitation and the ground coupling by deconvolving the motion recorded at different levels in the building, and apply this to record-ings of the motion in the Robert A. Millikan Library in Pasadena, California. The waveforms obtained from deconvolution with the motion in the top floor show a superposition of one upgoing and one downgoing wave. The waveforms obtained by deconvolution with the motion in the basement can be formulated either as a sum of upgoing and downgoing waves, or as a sum over normal modes. Since these deconvolved waves for late time have a monochromatic character, they are most easily analyzed with normal-mode theory. For this building we estimate a shear velocity c = 322 m/s and a quality factor Q = 20. These values explain both the propagating waves as well as the normal modes. We show for this application of seismic interferometry that deconvolution of waveforms is superior to correlation.
The mode summation method and a finite difference technique are applied to investigate the spectral ratio between the horizontal and vertical components (H/V ratio) of ambient vibrations and to explore the variation of the resonance frequency and the amplitude and shape of polarization as a function of the structure and the source positions. Layered structural models are used by assuming a large number of sources distributed around a receiver, with shallow source depths that are randomly assigned. We identify stable parts of the H/V ratios that are independent of the source distance and are dominated by the ellipticity of the fundamental-mode Rayleigh wave in the frequency band between the fundamental frequency of resonance of the unconsolidated sediments and the first minimum of the average H/V ratio. The ellipticity in this frequency band is determined by the layering of the sediments.
The numerical simulations are compared with observations at a site where the thickness and velocity structure of the unconsolidated sediments are known from S-wave and surface wave measurements. Two methods are applied to compute the H/V ratio, the classical method in the frequency domain and a method based on frequency–time analysis that allows us to locate P–SV wavelets in the time-series. The main problem in comparing synthetics with observations is the contribution of SH waves in the observed H/V ratios. We propose a method to minimize these effects and the effects of the superposition of different incoming P–SV waves. An inversion scheme is applied to the stable parts of the observed H/V ratio, based on a genetic algorithm, to retrieve the S-wave velocity structure from a single ambient vibration record.
Ambient seismic noise measurements were conducted inside the Holweide Hospital (Cologne) for checking whether its frequencies of vibration fall into the range where soil amplification is expected. If this is the case, damage might increase in case of an earthquake due to an amplified structural response of the building. Two different techniques were used: the ratio between the horizontal and vertical components of the spectra recorded at stations located inside the building and the ratio between the corresponding components of the spectra recorded simultaneously inside the building and at a reference station placed outside. While the former method might be preferred because of less equipment involved, the latter has the advantage of producing more stable results and deleting automatically the influence of the sedimentary cover, which might obscure some eigenfrequencies of vibration of the building. An independently performed finite-element analysis of the hospital showed a good correlation between measured and calculated eigenmodes.
This article is of an inter-disciplinary nature, relevant to the fields of both earth sciences and historiography, which come
together in the investigation of long-term earthquake hazard. The paper emphasises the need for systematic and consistent
analysis of historical earthquake data and sets out an example for such a task. The results from the historical study of earthquakes
will be of value to earth scientists and engineers only when historical information is converted into “numbers” representing
epicentral location and magnitude of the events, accompanied by an estimate of the reliability of their assessment. However,
as we go further back in time before our era, the historical record gradually disappears and the archaeological record takes
over. Unfortunately, the archaeological record is too coarse and ambiguous, without any precise internal archaeological indicators.
Dating is based on, or influenced by the very few historical records, such as in the Bible and inscriptions, which provide
an example of how their assumed accuracy may influence archaeologists' interpretation and dating. Quite often this develops
into a circular process in which archaeological assumptions or theories are transformed into facts and used by earth scientists
to confirm the dates and size of their proposed events. In this article we discuss the problems that arise when Biblical and
archaeological information is used at face value to assess earthquakes in the Holy Land. This combination may produce earthquakes
of hypothetical location and of grossly exaggerated magnitude with consequences for the assessment of seismic hazard.
A high-resolution Holocene seismic history of the Dead Sea Transform (DST) is established from laminated sedimentary cores recovered at the shores of the Dead Sea. Radiocarbon dating and annual laminae counting yield excellent agreement between disturbed sedimentary structures (identified as seismites) and the historical earthquake record: All recent and historical strong events of the area were identified, including the major earthquakes of A.D. 1927, 1837, 1212, 1033, 749, and 31 B.C. The total of 53 seismites recognized along the entire Holocene profile indicate varying recurrence intervals of seismic activity between a few and 1000 years, with a conspicuous minimum rate at 2100–31 B.C. and a noticeable maximum during the past six to eight centuries. Most of the epicenters of the correlated earthquakes are situated very close to the Dead Sea (within 150 km) or up to 400 km north of it along the DST. Between 1000 B.C. and A.D. 1063, and from A.D. 1600 to recent time the epicenters are all located on the northern segment of the DST, whereas prior to 1000 B.C. and between A.D. 1000 and 1600 they appear to scatter along several segments of the DST. We establish how the local intensity exerts a control on the formation of seismites. At historically estimated intensities greater than VII, all well documented earthquakes are correlated, whereas at intensities smaller than VI none are matching.The periods with enhanced earthquake rate along the DST correlate with those along the North Anatolian Fault as opposed to the intervening East Anatolian Fault. This may indicate some elastic coupling on plate-boundary scale that may also underlie escape and extrusion tectonics, typical of continental collision.
The citadel of Machupicchu is probably the most famous Inca heritage site in Peru. Considering the seismically active region, this research is an attempt to perform a seismic risk analysis of the heritage structures at Machupicchu. A systematic approach is adopted for this purpose. Characteristic seismicity of the region, where these historical constructions are located, is discussed based on the seismic hazard analysis. Evaluation of the vulnerability of the structures under the prevalent earthquake hazard is another important aspect essential for risk analysis. As a first step to proper understanding of the seismic behavior of these heritage structures, typical elements of Inca construction are studied by simple analytical models to verify basic aspects of structural integrity. The possibility that peak ground acceleration corresponding to even relatively low hazard may produce instability in some structural components like gable walls was noted. In view of this preliminary result, attempt was made to identify the dynamic characteristics of typical buildings units from more detailed investigation. This forms part of the outcome from the field study program, which included microtremor measurement of free field as well as typical constructions, planned and undertaken by the authors. The results of the microtremor measurements are utilized to estimate the dynamic characteristics of the Inca stone structures. That is, the analytical results are compared with the measurements to calibrate the analytical model. Since microtremor measurements involve very small displacements, the characteristics of stones structures thus obtained correspond to elastic behavior applicable to small strain condition. Based on this scheme, an approach has been proposed to evaluate the seismic behavior and hence the seismic vulnerability of these structures. The procedure also permits identification of the probable mode of failure of the structures concerned.
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1 – Virtual exterior view of the Basilica of the Holy Sepulchre and adjacent buildings from the NE obtained by a 3D laser scanner survey (courtesy of
Fig. 1 – Virtual exterior view of the Basilica of the Holy Sepulchre and adjacent buildings from the NE obtained by a 3D laser
scanner survey (courtesy of Prof. G. Tucci, Dipartimento di Costruzioni e Restauro, Università di Firenze).
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