Jf Lawrence

Stanford University | SU · Department of Geophysics

We use ambient-noise tomography to improve CVM-H11.9, a community velocity model of southern California. Our new 3D shear-velocity model with 0.05°x0.05° lateral and 1-km vertical blocks reveals new structure beneath the San Andreas Fault (SAF), Peninsular Ranges batholith (PRB), southern Sierra Nevada batholith (SNB) and the Salton Trough (ST). We...

Immediately following the Mw 7.2 Darfield, New Zealand, earthquake, over 180 Quake-Catcher Network (QCN) low-cost micro-electro-mechanical systems accelerometers were deployed in the Canterbury region. Using data recorded by this dense network from 2010 to 2013, we significantly improved the QCN rapid magnitude estimation relationship. The previous...

Over the past two decades, there have been several initiatives to create volunteer‐based seismic networks. The Personal Seismic Network, proposed around 1990, used a short‐period seismograph to record earthquake waveforms using existing phone lines (Cranswick and Banfill, 1990; Cranswick et al. , 1993). NetQuakes (Luetgert et al. , 2010) deploys tr...

The Quake‐Catcher Network (QCN) is an expanding seismic array made possible by thousands of participants who volunteered time and resources from their computers to record seismic data using low‐cost accelerometers (http://qcn.stanford.edu/; last accessed December 2014). Sensors based on Micro‐Electromechanical Systems (MEMS) technology have rapidly...

We retrieve P diving waves by applying seismic interferometry to ambient noise records observed at Long Beach, California, and invert travel times of these waves to estimate 3D P-wave velocity structure. The ambient noise is recorded by a 2D dense and large network, which has about 2500 receivers with 100-m spacing. Compared to surface-wave extract...

Meteoroid impacts over millions to billions of years can produce a highly fractured and heterogeneous megaregolith layer on planetary bodies such as the Moon that lack effective surface recycling mechanisms. The energy from seismic events on these bodies undergoes scattering in the fractured layer(s) and generates extensive coda wave trains that fo...

The Bío Bío region of Chile experienced a vigorous aftershock sequence following the 2010 February 27 Mw 8.8 Maule earthquake. The immediate aftershock sequence was captured by two temporary seismic deployments: the Quake Catcher Network Rapid Aftershock Mobilization Program (QCN RAMP) and the Incorporated Research Institutions for Seismology CHile...

We evaluate Rayleigh wave group velocity dispersion (5-40s) around the Yellowstone Volcano Field with ambient noise tomography, measured from vertical component noise correlation functions. We include broadband data from 239 seismic stations (1999-2012), including USArray's Transportable Array and the Noise Observatory for Imaging the Subsurface be...

We use a modified phonon synthetic seismogram method to investigate the effects of laterally varying megaregolith thickness on the propagation of seismic energy and on the resulting seismic signals recorded at various epicentral distances from the source. We show that receivers located in large impact structures, with thin crust and thinner megareg...

We test the feasibility of rapidly detecting and characterizing earthquakes with the Quake-Catcher Network (QCN) that connects low-cost microelectromechanical systems accelerometers to a network of volunteer-owned, Internet-connected computers. Following the 3 September 2010 M 7.2 Darfield, New Zealand, earthquake we installed over 180 QCN sensors...

Several groups are implementing low-cost host-operated systems of strong-motion accelerographs to support the somewhat divergent needs of seismologists and earthquake engineers. The Advanced National Seismic System Technical Implementation Committee (ANSS TIC, 2002), managed by the U.S. Geological Survey (USGS) in cooperation with other network ope...

[1] The ambient noise correlation function (NCF) calculated between seismic stations contains, under appropriate conditions, accurate travel time information. However, NCF amplitudes are highly debated due to noise source intensity and distribution, seismic intrinsic attenuation, scattering, and elastic path effects such as focusing and defocusing....

We use common conversion point (CCP) stacking of Ps receiver functions to image the crustal structure and Moho of the Garhwal Himalaya of India. Our seismic array of 21 broadband seismometers spanned the Himalayan thrust wedge at 79–80°E, between the Main Frontal Thrust and the South Tibet Detachment, in 2005–2006. Our CCP image shows the Main Hima...

1] We use ambient-noise tomography to map regional differences in crustal Rayleigh-wave group velocities with periods of 8–40 s across north Tibet using the International Deep Profiling of Tibet and the Himalaya phase IV arrays (132 stations, deployed for 10–24 months). For periods of 8–24 s (sensitive to midcrustal depths of ~5–30 km), we observe...

The effects of various lunar scattering structures are investigated by studying the decay characteristics of synthetic signals generated with the phonon method.

We investigate the intrinsic attenuation and scattering properties of the Moon by parameterizing the coda decay of 369 higher-quality lunar seismograms from 72 events via their characteristic rise and decay times. We investigate any dependence of the decay times on source type, frequency, and epicentral distance. Intrinsic attenuation, scattering,...

Following the 4 September 2010 M7.1 Darfield earthquake in New Zealand, we initiated a QCN Rapid Aftershock Mobilization Project (RAMP). We rapidly installed 180 low-cost 14-bit USB Micro-Electro-Mechanical Systems (MEMS) accelerometers in less than a week in order to record aftershocks as many aftershocks as possible. Using data recorded by these...

We model lunar seismic waveforms in a highly heterogeneous media and investigate suites of scattering models of the Moon. The decay parameters of the synthetic coda are compared to those of the Apollo lunar seismic dataset.

Here, we evaluate the improvement in noise correlation functions (NCFs) gained by dividing ambient seismic records into shorter, overlapping time windows before correlation and stacking (Welch's method). We compare waveform convergence of short duration NCF stacks (e.g. 2, 5, 15 and 50 d stacks) towards the long-term (365 d) NCF stack. We observe s...

The Quake-Catcher Network (QCN) uses low-cost sensors connected to volunteer computers across the world to monitor seismic events. The location and density of these sensors' placement can impact the accuracy of the event detection. Because testing different special arrangements of new sensors could disrupt the currently active project, this would b...

We assess local site response in the Bíobío region of Chile utilizing seismograms recorded by the Quake-Catcher Network (QCN) micro-electro-mechanical system (MEMS) accelerometers during the aftershock sequence that followed the February 27, 2010 Mw 8.8 Maule earthquake. The earthquakes were captured by over 70 QCN low-resolution (10, 12, and 14-bi...

The 3 September 2010 Mw 7.1 Darfield earthquake was felt over 900 km from the source. The maximum felt-intensity was estimated to be at Modified Mercalli Intensity (MMI) 9 and measured near-field accelerations were found to exceed 1 g. The mainshock damaged or destroyed over 100,000 buildings and spatially variable effects (such as liquefaction, sl...

A metamorphic core complex is a structure that unroofs high-grade, ductilely deformed crust. Core complexes have been well studied, but the process of their formation is controversial. The Ruby Mountains Core Complex (RMCC), located in the Basin-and-Range region in northeastern Nevada, is a classic example of a metamorphic core complex. It has been...

This study examines the notion of generating 4D ambient noise tomographic images that have the potential to observe temporal variations in a given study region. Evaluation of the ambient seismic field provides a unique opportunity to study geological process in action. In geologically active regions, the time lag of the ambient Noise Correlation Fu...

Following the 4 September 2010 M7.1 Darfield earthquake in New Zealand, we initiated a QCN Rapid Aftershock Mobilization Program (RAMP). We rapidly installed 180 low-cost 14-bit USB accelerometers to record aftershocks. We began testing our rapid earthquake detection and characterization program that we had first experimented with following our RAM...

In January 2011, 42 broadband seismic stations provided by the PASSCAL pool and on loan from Caltech were deployed across the Salton Trough in southernmost California. These stations will continue to record continuous seismic data for a period of 18 months as part of the Salton Seismic Imaging Project. 36 of the 42 stations were deployed along a li...

In this study we image the Moho beneath the Himalaya of Garhwal, India (at approximately 79°E) using common conversion point (CCP) stacking of receiver functions (RFs). We calculate RFs using iterative time-domain deconvolution on a catalog of 450 events recorded on a linear array of 21 broadband seismometers operated for 21 months in 2005-2006 by...

The Kinect technology allows for hands-free game play, greatly increasing the accessibility of gaming for those uncomfortable using controllers. How it works is the Kinect camera transmits invisible near-infrared light and measures its "time of flight" to reflect off an object, allowing it to distinguish objects within 1 centimeter in depth and 3 m...

The Quake-Catcher Network (QCN) is a collaborative initiative for developing the world's largest, low-cost strong-motion seismic network by utilizing sensors in and attached to volunteer internet-connected computers. QCN is not only a research tool, but provides an educational tool for teaching earthquake science in formal and informal environments...

Accelerometers based on low-cost micro-electro-mechanical systems (MEMS) have improved swiftly, making the rapid deployment of dense seismic arrays possible. For example, the Quake-Catcher Network (QCN) makes use of MEMS-based tri-axial sensors installed in homes and businesses to record earthquakes, with almost 2000 participants worldwide. QCN uti...

The use of the ambient seismic field (ASF) to extract Earth's response has received significant attention in the last several years. Multiple studies demonstrate the utility of the ASF for estimating high-resolution velocity models in various locations. In this paper, we discuss the amplitude information carried by the ASF. Amplitude information in...

Rapid detection and characterization of earthquakes is essential for earthquake early warning systems, which have the potential to alert nearby populations about the approach of potentially damaging seismic waves ( e.g. , Allen and Kanamori 2003; Kanamori 2005). In addition, minimizing the time required to estimate the extent and amplitude of groun...

1] We show that the spatial coherency of the ambient seismic field can be used for attenuation tomography in the western United States. We evaluate the real portion of the spatial coherency with an elastic geometric spreading term (a Bessel function) and a distance dependent decay (an attenuation coefficient). In order to invert the spatial coheren...

Recent advances in micro-electro-mechanical systems (MEMS) sensing and distributed computing techniques have enabled the development of low-cost, rapidly deployed dense seismic networks. The Quake-Catcher Network (QCN) uses triaxial MEMS accelerometers installed in homes and businesses to record moderate to large earthquakes. Real-time acceleration...

We characterize long-duration APSE lunar seismic codas via their rise times and their characteristic decay times. We compared them to synthetically generated signals in order to indentify suites of interior structure models compatible with the data.

Ground motion prediction is traditionally estimated in seismic hazard analysis using parametric scaling relations, which are often referred to as "attenuation relations." Increasingly, seismologists are turning to simulation-based hazard analysis. There are at least two reasons for this. First, it allows seismologists to overcome the scarcity of da...

In 2009 and 2010 we (re)deployed 12 broadband seismic stations around Yellowstone for three months each year. The goal of the project is to collect data for 4D ambient noise tomography. In phase one, we generate a high-resolution group velocity image Yellowstone region using ambient noise. We generate empirical Green's functions (EGFs) by stacking...

The Quake-Catcher Network (QCN) involves the community in strong motion data collection by utilizing volunteer computing techniques and low-cost MEMS accelerometers. Volunteer computing provides a mechanism to expand strong-motion seismology with minimal infrastructure costs, while promoting community participation in science. Micro-Electro-Mechani...

This study examines under which input parameters the cross correlation of ambient seismic noise generates stable empirical Green's functions (EGFs) with a minimum quantity of data. We evaluate the effects of varying the duration of correlated ambient data windows, the over-sampling, and the threshold for automatically removing noise data ``contamin...

Using common conversion point (CCP) stacking of teleseismic receiver functions (RFs), we image the Moho and Main Himalayan Thrust (MHT) beneath the Garhwal Himalaya (Alaknanda Valley, Uttaranchal, India). Beneath the Main Frontal Thrust (southern margin of the Himalaya), we image the Moho at a depth of 40 km, increasing to a depth of 55 km beneath...

Increased monitoring of civil structures for response to earthquake motions is fundamental to reducing seismic risk. Seismic monitoring is difficult because typically only a few useful, intermediate to large earthquakes occur per decade near instrumented structures. Here, we demonstrate that the impulse response function (IRF) of a multistory build...

AGU Meeting of the Americas

Rapid and accurate assessment of source characteristics of moderate to large earthquakes is extremely useful for hazard assessment and to guide response of emergency services. Using the back projection method (BPM) it is possible to obtain an image of the source rupture process rapidly. The potential of the method in identifying the rupture propaga...

We investigate the seismic scattering effects of a highly heterogeneous regolith layer on the Moon, and how shallow heterogeneity effects high-frequency seismograms.

The Quake-Catcher Network (QCN) is breaking new ground in seismology by combining new micro-electro-mechanical systems (MEMS) technology with volunteer seismic station distributed computing. Rather than distributing just computations, the QCN allows volunteers to participate in scientific data collection and computation. Using these innovative tool...

Increased monitoring of civil structures for response to earthquake motions is fundamental for reducing seismic hazard. Seismic monitoring is difficult because typically only a few useful, intermediate to large earthquakes occur per decade near instrumented structures. Here we demonstrate that the impulse response function (IRF) of a multi-story bu...

The goal of the Quake-Catcher Network (QCN) is to dramatically increase the number of strong-motion observations by exploiting recent advances in sensing technologies and cyberinfrastructure. Micro-Electro-Mechanical Systems (MEMS) triaxial accelerometers are very low cost (50-100), interface to any desktop computer via USB cable, and provide high-...

Modeling wave propagation through the complex geology of the crust is one of the foremost challenges to a physics-based approach to seismic hazard analysis, largely because we lack the complete description of elastic and anelastic structure needed for accurate ground motion simulations. We use the ambient seismic field to improve these simulations...

The Modeling and Educational Demonstrations Laboratory (MEDL) at the University of California, Los Angeles has developed a fourth version of the Elastic Rebound Strike-slip (ERS) Fault Model to be used to educate students and the general public about the process and mechanics of earthquakes from strike-slip faults. The ERS Fault Model is an interac...

The Quake-Catcher Network (QCN) is a volunteer computing seismic network that engages citizen scientists, teachers, and museums to participate in the detection of earthquakes. In less than two years, the network has grown to over 1000 participants globally and continues to expand. QCN utilizes Micro-Electro-Mechanical System (MEMS) accelerometers,...

We performed wave-equation migration (WEM) of teleseismic earthquakes from a range of backazimuths to image the main features of the Himalayan thrust belt. To date we have successfully imaged the Main Himalayan Thrust (MHT), and done so with greater resolution than we found using more-common teleseismic imaging methods (namely, CCP stacking of dept...

Tomographic imaging of the Earth's elastic wave velocities has improved significantly over time, due to increasing density of data from large seismic networks (USArray, Hi-net, etc). The uneven distribtion of earthquakes inside the Earth, however, makes it difficult to obtain reliable models. Use of the seismic ambient field for tomography has help...

USArray provides an unprecedented data set with which to examine the anelastic structure beneath the continental United States. Here, we present a body wave attenuation measurement technique, inversion methods, and resultant quality factor models. For direct comparison, we also invert equivalent travel-time data for velocity structure. In addition...

We present a new technique for predicting the earthquake responses of various structures, and we demonstrate its effectiveness by applying the method to several buildings, including several newly instrumented buildings around the Stanford University campus. While the use of ambient noise recordings to determine structural qualities of buildings is...

Seismic shear-wave velocities are sensitive to the partial melts that should be present in the Himalayan orogen if low-viscosity channel flow is active at the present day. We analyzed regional earthquakes in the western Himalaya and Tibet recorded on 16 broadband seismometers deployed across the NW Indian Himalaya, from the Indian platform to the K...

Cross correlation of the ambient seismic field is now routinely used to measure seismic wave travel times; however, relatively little attention has been paid to other information that could be extracted from these signals. In this paper we demonstrate the relationship between the spatial coherency of the ambient field and the elastodynamic Green's...

The Main Ethiopian Rift (MER) is a classic narrow rift that developed in hot, weak lithosphere, not in the initially cold, thick, and strong lithosphere that would be predicted by common models of rift mode formation. Our new 1-D seismic velocity profiles from Rayleigh wave/receiver function joint inversion across the MER and the Ethiopian Plateau...

In this study, we jointly invert two previously unpaired seismic data types, receiver functions and ambient noise dispersion, to determine a high-resolution estimate of the earth structure. Jointly inverting receiver functions and surface wave dispersion is a well-tested technique (e.g., Juliá et al. 2000) that provides significantly higher quality...

Rapid and accurate assessment of source (rupture) characteristics of a moderate to large earthquake can be used for hazard assessment and guidance of emergency services, which are critical for efficient rescue efforts to mitigate economic damages and/or loss of human lives, in addition to providing valuable inputs to scientific community regarding...

The Main Ethiopian Rift (MER) is a classic example of a narrow rift, but a synthesis of our results from the EAGLE (Ethiopia-Afar Geoscientific Lithospheric Experiment Phase I broadband experiment) and from the EBSE experiment (Ethiopia Broadband Seismic Experiment) suggests the MER formed in thin, hot, weak continental lithosphere, in strong contr...

Recent advances in distributed computing provide exciting opportunities for seismic data collection. We are in the early stages of implementing a high density, low cost strong-motion network for rapid response and early warning by placing accelerometers in schools, homes, offices, government buildings, fire houses and more. The Quake Catcher Networ...

The Transantarctic Mountains are a major rift-related mountain belt bisecting the Antarctic continent. The range is located on the tectonic boundary between non-cratonic West and cratonic East Antarctica. Formation of the mountain range and a possible relation with the West Antarctic Rift system are unclear. In this study, we find a new explanation...

DOI = 10.3126/hjs.v5i7.1240 Himalayan Journal of Sciences Vol.5(7) (Special Issue) 2008 p.33

We invert differential SdS-SS traveltime residuals measured from stacked waveforms and finite-frequency sensitivity kernels for topography on the 410- and 660-km discontinuities. This approach yields higher resolution images of transition zone thickness than previous stacking methods, which simply average/smooth over topographic features. Apparent...

We characterize transition-zone seismic wave propagation by mapping and calibrating the travel-time and amplitude behavior of P waves traveling through the transition zone at epicentral distances from 13 to 30 degrees and modeling the triplications resulting from the 410- and 660-km discontinuities. We have built an online database of waveforms fro...

A fundamental question regarding the dynamics of mantle convection is whether some intraplate volcanic centers, known as “hotspots,” are the surface manifestations of hot, narrow, thermally driven upwellings, or plumes, rising from the lower mantle. Shown here is a global negative correlation between the thickness of the mantle transition zone (nea...

We present P- and S-wave attenuation models for western North America, using the latest up-to-date EarthScope USArray seismic data. Tomographic models of P and S waves are done separately, using a least-squares inversion with a volume parameterization beneath the USArray stations. We find that there is strong correlation between the P and S models,...

We propose to implement a high density, low cost strong-motion network for rapid response and early warning by placing sensors in schools, homes, and offices. The Quake Catcher Network (QCN) will employ existing networked laptops and desktops to form the world's largest high-density, distributed computing seismic network. Costs for this network wil...

The Transantarctic Mountains are a non-compressional mountain belt located on the tectonic boundary between cratonic East Antarctica and non-cratonic West Antarctica. Formation of this mountain belt and a possible relation with the West Antarctic Rift system are still debated. Here we suggest a new explanation for uplift of the mountains, formation...

Crust and upper mantle structure beneath the Transantarctic Mountains, East Antarctic Craton, and the West Antarctic rift system (WARS) in the vicinity of Ross Island, Antarctica has been imaged in several ways using data collected by the TAMSEIS project. Results from body and surface wave tomography, receiver function analysis, and attenuation stu...

There is currently a debate over whether the mantle source regions of "hotspots" are hotter than the ambient mantle. Some of the assumptions involved in estimating mantle temperatures have been questioned, leading to the suggestion that temperatures beneath "hotspots" may fall within the range of that beneath mid-ocean ridges. If "hotspots" are not...

This study uses seismic receiver functions, surface wave phase velocities, and airborne gravity measurements to investigate the structure of the Transantarctic Mountains (TAM) and adjacent regions of the Ross Sea (RS) and East Antarctica (EA). Forty-one broadband seismometers deployed during the Transantarctic Mountain Seismic Experiment provide ne...

1] Systematic stacks of P wave receiver functions (Pds) for 118 global seismic stations yield new transition zone thickness (W TZ) estimates, as measured by the difference in depths between the 410-and 660-km mantle discontinuities. The receiver functions are computed from high signal-to-noise records of earthquakes between 1976 and 2002 recorded a...

This study analyzes Rayleigh wave phase velocities from the Ross Sea (RS) region of the West Antarctica rift system, the Transantarctic Mountains (TAMs), and part of East Antarctica (EA). The Transantarctic Mountain Seismic Experiment deployed 41 three-component broadband seismometers, which provide new data for high-resolution two-dimensional maps...

1] We measure seismic attenuation beneath North America using waveform cross-correlation and cluster analysis, and obtain images of the laterally varying anelastic structure of the upper mantle. Cluster analysis improves attenuation measurements by systematically comparing only highly similar waveforms, which reduces bias from scattering, direction...

This study examines teleseismic S-wave attenuation variations between the Ross Sea in West Antarctica and Vostok Subglacial Highlands in East Antarctica. These analyses indicate that deltat* is ~1 second greater beneath the Ross Sea than East Antarctica, with the transition occurring beneath the Transantarctic Mountains. While the structure is non-...

We employ a niching genetic algorithm to invert ∼30,000 differential ScS/S attenuation values for a new spherically symmetric radial model of shear quality factor (Qμ) with high sensitivity to the lower mantle. The new radial Qμ model, QLM9, possesses greater sensitivity to Qμ at large mantle depths than previous studies. On average, lower mantle Q...

We use seismic attenuation tomography to identify a region at the top of the lower mantle that displays very high attenuation consistent with an elevated water content. Tomography inversions with >80,000 differential travel-time and attenuation mea- surements yield 3D whole-mantle models of shear velocity (VS) and shear quality factor (Qx). The glo...

Using the first global whole-mantle D model of shear quality factor, we identify a large region at the top of Earth's lower mantle with unusually high seismic attenuation. This anomaly, found down-dip of western Pacific subduction zones 700-1500 km beneath eastern Asia, is best explained by a 10-fold increase in water content. The anomaly occupies...

We use teleseismic receiver function and surface wave phase velocities to model the seismic velocity structure of the crust and upper mantle between the Ross Sea and Vostok Subglacial Highlands. The West Antarctic Rift System (WARS) has a thinner crust (~20 km) and slower seismic mantle velocities than East Antarctica (EA). Attenuation of shear bod...

We present a three-dimensional tomographic model of the seismic shear wave attenuation in the mantle. The model was obtained from all available digital broadband records during 1990-2001. The data consist of over 90,000 differential attenuation measurements of ScS-S, SS-S, ScS-SS, S-S, sScS-sS, sSS-sS phase pairs. The use of differential measuremen...

We invert over 90,000 differential travel-time and attenuation measurements for 3D whole-mantle velocity (V) and quality factor (Q) models with identical resolution. By comparing models of velocity and quality factor obtained from measurements of SH and SV waves, we calculate velocity anisotropy and quality factor anisotropy. The resolution of each...