A5063035701- Seismic Waves and Analysis
- Seismology and Earthquake Studies
- earthquake and tectonic studies
- Seismic Performance and Analysis
- Earthquake Detection and Analysis
- Structural Health Monitoring Techniques
- Seismic Imaging and Inversion Techniques
- Anomaly Detection Techniques and Applications
- Geophysics and Sensor Technology
- High-pressure geophysics and materials
- Wind and Air Flow Studies
- Disaster Management and Resilience
- Geophysical Methods and Applications
- Landslides and related hazards
- Structural Response to Dynamic Loads
- Icing and De-icing Technologies
- Vibration Control and Rheological Fluids
- Geomagnetism and Paleomagnetism Studies
- Time Series Analysis and Forecasting
- History and Developments in Astronomy
- Public Relations and Crisis Communication
- Cinema and Media Studies
- Soil Mechanics and Vehicle Dynamics
- Data-Driven Disease Surveillance
- Coastal and Marine Dynamics
United States Geological Survey
2015-2025
Earthquake Science Center
2013-2025
Southern California Earthquake Center
2017-2024
Menlo School
2017-2019
Stanford University
2010-2014
Strong spatial variation of rupture characteristics in the moment magnitude (M(w)) 9.0 Tohoku-Oki megathrust earthquake controlled both strength shaking and size tsunami that followed. Finite-source imaging reveals consisted a small initial phase, deep for up to 40 seconds, extensive shallow at 60 70 continuing lasting more than 100 seconds. A combination dipping fault compliant hanging wall may have enabled large slip near trench. Normal faulting aftershocks area high suggest dynamic...
The NGA-West2 project is a large multidisciplinary, multi-year research program on the Next Generation Attenuation (NGA) models for shallow crustal earthquakes in active tectonic regions. has been coordinated by Pacific Earthquake Engineering Research Center (PEER), with extensive technical interactions among many individuals and organizations. addresses several key issues ground-motion seismic hazard, including updating NGA database magnitude range of 3.0–7.9; prediction equations (GMPEs)...
We introduce a community stress drop validation study using the 2019 Ridgecrest, California, earthquake sequence, in which researchers are invited to use common dataset independently estimate comparable measurements variety of methods. Stress is change average shear on fault during rupture, and as such key parameter many ground motion, rupture simulation, source physics problems science. Spectral commonly estimated by fitting shape radiated energy spectrum, yet estimates for an individual...
[1] We apply empirical Green's function coda-based analysis to four earthquake sequences in Japan that span a magnitude range of 1.8 6.9, measure radiated energy, corner frequency and stress drop. find no systematic dependence apparent or drop on seismic moment for these sequences, they both are log-normally distributed; however, we identify several anomalous events - energetic enervated show sharply different spectral signatures from the rest population. These indicate much variation is...
In only rare cases will earthquake early warning systems be able to provide useful warnings for high levels of ground motion.
Abstract We explore how accurate earthquake early warning (EEW) can be, given our limited ability to forecast expected shaking even if the source is known. Because of strong variability ground motion metrics, such as peak acceleration (PGA) and velocity (PGV), we find that correct alerts (i.e., accurately estimate will be above a predetermined damage threshold) are not most common EEW outcome when magnitude location determined. Infrequently, results in user receiving false alert because...
First posted October 2, 2018 For additional information, contact: Earthquake Science Center-Pasadena Field OfficeU.S. Geological Survey525 South Wilson Ave.Pasadena, CA 91106-3212 The U.S. Survey (USGS), along with partner organizations, has developed an earthquake early warning (EEW) system called ShakeAlert for the highest risk areas of United States: namely, California, Oregon, and Washington. purpose is to reduce impact earthquakes save lives property by providing alerts institutional...
Residuals between ground‐motion data and prediction equations (GMPEs) can be decomposed into terms representing earthquake source, path, site effects. These cast in of repeatable (epistemic) residuals the random (aleatory) components. Identifying leads to a GMPE with reduced uncertainty for specific site, or path location, which turn yield lower hazard level at small probabilities exceedance. We illustrate schematic framework this residual partitioning dataset from ANZA network, straddles...
As ShakeAlert, the earthquake early warning system for West Coast of U.S., begins its transition to operational public alerting, we explore how post-alert messaging might represent performance. Planned can provide timely, crucial information both emergency managers and ShakeAlert operators as well calibrate expectations among various publics or user groups inform their responses future alerts. There is a concern scientists that false alerts may negatively impact trust in system, so quickly...
The seismic coda consists of scattered waves that leave the earthquake source in a variety directions. averaging radiation results leads to stable ground motion spectra we use as basis for robust measurement radiated wave energy. We apply an empirical Green's function (EGF) method order investigate scaling correct path effects earthquakes by using stack closely located, small EGF. this approach four sequences western North America span magnitude range from M w 3.0– 7.1. Our estimates scaled...
The Next Generation Attenuation‐West 2 (NGA‐West 2) 2014 ground‐motion prediction equations (GMPEs) model ground motions as a function of magnitude and distance, using empirically derived coefficients (e.g., Bozorgnia et al. , 2014); such, these GMPEs do not clearly employ earthquake source parameters beyond moment ( M ) focal mechanism. To better understand the magnitude‐dependent trends in GMPEs, we build comprehensive source‐based to explain dependence peak acceleration velocity NGA‐West...
We estimate the a rms‐stress drop, ![Graphic][1] , (Hanks, 1979) using acceleration time records of 59 earthquakes from two earthquake sequences in eastern Honshu, Japan. These acceleration‐based static stress drops compare well to calculated for same events by Baltay et al. (2011) an empirical Green’s function (eGf) approach. This agreement supports assumption that histories bandwidth between corner frequency and maximum observed can be considered white, Gaussian, noise. Although...
The M w 6.0 South Napa earthquake, which occurred at 10:20 UTC 24 August 2014 was the largest earthquake to strike greater San Francisco Bay area since w 6.9 1989 Loma Prieta earthquake. rupture from this right‐lateral propagated mostly unilaterally north and up‐dip, directing strongest shaking toward city of Napa, where peak ground accelerations (PGAs) between 45% g 61% were recorded modified Mercalli intensities (MMIs) VII–VIII reported. Tectonic surface with dextral slip up 46 cm observed...
ABSTRACT 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 southern California. The data are a combination Next Generation Attenuation-West2 project, 2019 Ridgecrest earthquakes, and about 10,000 newly processed records. estimate an iterative mixed-effects residuals partitioning approach, accounting for azimuthal variations anelastic attenuation potential bias due to spatial clusters...
Abstract We examine how the choice of ground-motion-to-intensity conversion equations (GMICEs) in earthquake early warning (EEW) systems affects resulting alert regions. find that existing GMICEs can underestimate observed shaking at short rupture distances or overestimate extent low-intensity shaking. Updated remove these biases would improve accuracy regions for ShakeAlert EEW system West Coast United States. uses ground-motion prediction (GMPEs), which calculate spatial distributions peak...
Several rupture directivity models (DMs) have been developed in recent years to describe the near-source spatial variations ground-motion amplitudes related propagation of along fault. We recently organized an effort toward incorporating these effects into US Geological Survey (USGS) National Seismic Hazard Model (NSHM), by first evaluating community’s work and potential methods implement adjustments probabilistic seismic hazard analysis (PSHA). Guided this evaluation comparison among...
Abstract “When will the Big One happen?” is a question that people often have for earthquake scientists. But while waiting “Big One” to occur, usually experience frightening or damaging shaking from multiple relatively smaller-magnitude earthquakes. Given this context, it raises question: “Where does most of damage come from?” Could smaller, yet more frequent, earthquakes account majority reported impactful shaking? To explore question, we consider reports and felt experiences catalog...
ABSTRACT The ShakeAlert earthquake early warning (EEW) system partners along with U.S. Geological Survey (USGS) licensed operators deliver EEW alerts to the public and trigger automated systems when a significant is expected impact California, Oregon, or Washington. ShakeAlert’s primary goal provide usable times before arrival of damaging shaking. most likely achieve this in large-magnitude earthquakes. In recent years, has gone through series upgrades its underlying scientific algorithms...
Research Article| October 16, 2018 Ground Motions from the 7 and 19 September 2017 Tehuantepec Puebla‐Morelos, Mexico, Earthquakes Valerie J. Sahakian; Sahakian aU.S. Geological Survey Earthquake Science Center, 345 Middlefield Road, MS 977, Menlo Park, California 94025, vjs@uoregon.edueNow at Department of Earth Sciences, University Oregon, 1585 East 13th Avenue, Eugene, Oregon 97403. Search for other works by this author on: GSW Google Scholar Diego Melgar; Melgar bDepartment 97403 Luis...
Research Article| July 24, 2018 Decomposing Leftovers: Event, Path, and Site Residuals for a Small‐Magnitude Anza Region GMPE Valerie Sahakian; Sahakian aEarthquake Science Center, U.S. Geological Survey, 345 Middlefield Road, MS 977, Menlo Park, California 94025, vjs@uoregon.edu Search other works by this author on: GSW Google Scholar Annemarie Baltay; Baltay Tom Hanks; Hanks Janine Buehler; Buehler bScripps Institution of Oceanography, University San Diego, 9500 Gilman Drive, La Jolla,...
Abstract We determine earthquake stress drops directly from the Arias intensity database of NGA‐West2. (Arias, 1970, https://www.osti.gov/biblio/4167721 ) is an engineering measure proportional to integral absolute value acceleration squared, over significant duration signal. As such, it closely related root mean square and can readily be connected drop (Hanks & McGuire, 1981, https://pubs.geoscienceworld.org/ssa/bssa/article/71/6/2071/102118/the-character-of-high-frequency-strong-ground...
Abstract Although small earthquakes are expected to produce weak shaking, ground motion is highly variable and there outlier that generate more shaking than expected—sometimes significantly more. We explore datasets of M 0.5–8.3 determine the relative impact frequent, smaller-magnitude rarely strong motion, rare, large always cause shaking. find natural variability combined with Gutenberg–Richter magnitude–frequency relationship, ensures most occurrences any come from smaller magnitude...
ABSTRACT Spectral source parameters used to estimate an earthquake’s stress drop (Δσ) can vary significantly across measurement approaches. The Statewide California Earthquake Center/U.S. Geological Survey Community Stress-Drop Validation Study was initiated compare parameter estimates, focusing initially on a dataset from the 2019 Ridgecrest earthquake sequence. As part of that validation effort, here we focus one potential uncertainty: whether spectral fitting approaches alone, applied...
Abstract To improve models of ground motion estimation and probabilistic seismic hazard analyses, the engineering seismology field is moving toward developing fully nonergodic models, specific for individual source‐to‐site paths. Previous work on this topic has examined systematic variations in ground‐motion along particular paths (from either recorded or simulated earthquake data) not included physical properties path. We present here a framework to include path properties, by seeking...
Abstract We test the Japanese ground‐motion‐based earthquake early warning (EEW) algorithm, propagation of local undamped motion (PLUM), in southern California with application to U.S. ShakeAlert system. In late 2018, began limited public alerting Los Angeles areas expected modified Mercalli intensity (IMMI) 4.0+ for magnitude 5.0+ earthquakes. Most EEW systems, including ShakeAlert, use source‐based methods: they estimate location, magnitude, and origin time an from P waves a ground‐motion...