A5023365788- earthquake and tectonic studies
- Seismic Waves and Analysis
- Seismology and Earthquake Studies
- High-pressure geophysics and materials
- Earthquake Detection and Analysis
- Seismic Imaging and Inversion Techniques
- Geophysics and Sensor Technology
- Seismic Performance and Analysis
- Structural Health Monitoring Techniques
- Geological and Geochemical Analysis
- Radiation Detection and Scintillator Technologies
- Advanced Algorithms and Applications
- Geophysical Methods and Applications
- Cryospheric studies and observations
- Geochemistry and Geologic Mapping
- Radioactive contamination and transfer
- Underwater Acoustics Research
- Landslides and related hazards
- Nuclear Physics and Applications
- Atmospheric and Environmental Gas Dynamics
- Geological and Geophysical Studies
- Reservoir Engineering and Simulation Methods
- Geophysics and Gravity Measurements
- Structural Analysis and Optimization
- Semiconductor Quantum Structures and Devices
Patrick Air Force Base
2019-2025
University of California, Berkeley
2008-2017
Berkeley Geochronology Center
2010
Geophysical Laboratory
2009
Lawrence Livermore National Laboratory
1985-2006
Lawrence Livermore National Security
1997-2000
Office of Scientific and Technical Information
2000
University of Southern California
1991-1995
We present a new method to estimate stable seismic source parameters, such as energy, moment, and Orowan stress drop, using regional coda envelopes from few one broadband station. use the compute path‐ site‐corrected moment‐rate spectra for 117 recent western United States earthquakes. Empirical Green's function corrections were applied our surface‐ body‐wave envelope measurements generate S ‐wave spectra. These provide stable, single‐station estimates of radiated energy E s moment M o that...
ABSTRACT We present initial findings from the ongoing Community Stress Drop Validation Study to compare spectral stress-drop estimates for earthquakes in 2019 Ridgecrest, California, sequence. This study uses a unified dataset independently estimate earthquake source parameters through various methods. drop, which denotes change average shear stress along fault during rupture, is critical parameter science, impacting ground motion, rupture simulation, and physics. Spectral drop commonly...
A new method recently developed by Hoshiba et al. (1991) was used to separate the effects of scattering Q −1 and intrinsic from an analysis S wave its coda in Hawaii, Long Valley, central California. Unlike Wu [1985], which involves integration entire energy, relies on energy for three successive time windows as a function hypocentral distance. Using fundamental separability source, site, path waves, we normalized each window many events recorded at stations common site source. We plotted...
Seismic discrimination of small-magnitude ( mb 0.5 Hz) regional measurements. In this study we evaluate the most promising short-period discriminants, P -wave to S phase-amplitude ratios and low- high-frequency spectral-amplitude ratios, for a data set from Nevada Test Site. The consist 130 underground nuclear explosions, one very large chemical explosion, 50 earthquakes, ranging magnitude 2 6, recorded at two broadband digital seismic stations operated by Lawrence Livermore National...
The use of local and regional S ‐wave coda is shown to provide stable amplitude ratios that better constrains source differences between event pairs. We first compared ratio performance near‐regional waves in the San Francisco Bay region for moderate‐sized events, then applied spectral method 1999 Hector Mine mainshock its larger aftershocks. find (1) average standard deviations using are ∼0.05 0.12, roughly a factor 3 smaller than direct ‐waves 0.2 < f 15.0 Hz; (2) M w 7.0 earthquake...
Abstract As part of the community stress-drop validation study, we evaluate uncertainties seismic moment M0 and corner frequency fc for earthquakes 2019 Ridgecrest sequence. Source spectra were obtained in companion article by applying spectral decomposition approach with alternative processing model assumptions. The objective present study is twofold: first, to quantify impact different assumptions on source parameters; second, use distribution values estimate an epistemic contribution...
We describe an empirical calibration method for obtaining stable seismic source moment-rate spectra derived from regional coda envelopes using broadband stations. The results of applying this yield that are more than any other direct-phase measure to date. procedure accounts all propagation, site, and S -to-coda transfer function effects. resultant coda-derived then used provide traditional band-limited magnitudes (e.g., M L , m b ), as well unbiased, unsaturated magnitude (moment magnitude,...
Abstract As part of the community stress-drop validation study initiative, we apply a spectral decomposition approach to isolate source spectra 556 events occurred during 2019 Ridgecrest sequence (Southern California). We perform multiple decompositions by introducing alternative choices for some processing and model assumptions, namely: three different S-wave window durations (i.e., 5 s, 20 variable between s); two attenuation models that account differently depth dependencies; site...
A multiple lapse time window analysis was applied to three‐component broadband seismograms recorded at five TERRAscope stations in southern California separate scattering and intrinsic attenuation. Seismic energies were integrated over three consecutive intervals: 0–15, 15–30, 30–45 s (measured from the S arrival) for approximately 30 earthquakes with hypocentral distances of less than 70 km each station. Using fundamental separability source, site, path effects coda waves, different...
We present two lines of evidence showing the ratio seismically radiated energy ( E R ) to seismic moment M o increases with increasing for crustal events spanning 5 orders in moment. This ratio, often referred as scaled (= / 0 has been elusive and subject recent debate within seismological community. Because significant frequency‐dependent corrections must be made account source path heterogeneity, it is not uncommon that estimates same event by different researchers have significantly...
ABSTRACT The determination of accurate apparent stress, radiated energy, corner frequency, and their scaling with magnitude remains one the most difficult seismological endeavors because complicated 3D Earth structure, complex rupture, limited broadband recordings. This study focuses on a comparison four separate state-of-the-art methods that aim to compare contrast common events using well-recorded 2019 Ridgecrest, California, sequence, which was motivated in large part by U.S. Geological...
Abstract A challenge in fully using distributed acoustic sensing (DAS) data collected from fiber-optic sensors is correcting the signals to provide quantitative true ground motion. Such corrections require considering coupling and instrument response issues. In this study, we show via comparison with geophone broadband seismometer that can use coda envelope calibration techniques obtain absolute moment magnitudes source spectra DAS data. Here, nodal geophones deployed as part of a geothermal...
Abstract In August and September of 1997, three 25-ton chemical explosions were detonated at nominal depths 550, 300, 50 m in boreholes the former Soviet test site Balapan, Kazakhstan. One objective this experiment was to evaluate effect differing source depth on regional wave field. Analysis seismic phases lead observation that P/S amplitude ratios 1- 5-Hz band increase as a function depth. However, frequencies greater than about 5 Hz, relative amplitudes P S waves remain approximately...
Abstract Following the work of Phillips (1985), we have computed site amplification factors for coda waves at many sites in Long Valley region eastern Sierra Nevada. We ratios amplitudes measured 15 stations and around caldera relative to a granitic site, MMPM, six frequency bands centered 1.5, 3.0, 6.0, 9.0, 12.0, 15.0 Hz. All station located within experienced large ground motion 1.5 3.0 Hz, ranging between five 17 times that reference site. However, higher frequencies, these same...
Abstract Site amplification factors at frequencies of 1.5, 3, 6, and 12 Hz were determined for 132 stations the USGS seismic network in central California from coda waves 185 local earthquakes this area using a recursive stochastic inversion method. We found that site station is systematically related to geology underlying station. The high young, Quaternary sediments decreases with increasing geologic age all between 1.5 Hz. rate decrease varies frequency where low shows faster than higher...
The scaling of earthquakes the Central Apennines (Italy) is investigated using broadband seismograms from Colfiorito sequence (4 ≤ M W 6). Our results are not consistent with self‐similar scaling, and can be described by following relationship: 0 ∝ f c −(3 + ɛ) , where ɛ = 1.7 ± 0.3. We speculate that dynamic fault lubrication fluid pressurization may responsible for such extreme behavior, use our calibration a weak‐motion‐based predictive relationship ground motion ( 4.1) up to ∼ 6 this region.
This study documents another unique property of local and regional shear‐wave coda: that scattering in the Earth's crust averages out source heterogeneities such as focal mechanism directivity. We consider two recent events which exhibited significant The first, an M w 4.2 Oakland hills, California strike‐slip event on July 20, 2007, resulted uncharacteristically large amounts damage Montclair south Berkeley neighborhoods, along strike north‐west hypocenter, but almost no to south‐east....
Based only on weak-motion data, we carried out a combined study region-specific source scaling and crustal attenuation in the Central Apennines (Italy). Our goal was to obtain reappraisal of existing predictive relationships for ground motion, test them against strong-motion data [peak acceleration (PGA), peak velocity (PGV) spectral (SA)] gathered during Mw 6.15 L'Aquila earthquake (2009 April 6, 01:32 UTC). The main shock not part study, validation an extrapolation one magnitude unit above...
SUMMARY Robustness of source parameter estimates is a fundamental issue in understanding the relationships between small and large events; however, it difficult to assess how much variability parameters can be attributed physical characteristics or uncertainties methods data used estimate values. In this study, we apply coda method by Mayeda et al. using calibration tool (CCT), freely available Java-based code (https://github.com/LLNL/coda-calibration-tool) obtain regional for Central Italy...
SUMMARY The United Kingdom (UK) experiences low-to-moderate levels of seismicity; only 12 onshore earthquakes with local magnitude (ML) ≥ 4.0 have been recorded in the past 20 yr. It is therefore difficult to estimate moment (Mw) using conventional tensor inversion for majority UK seismicity, resulting limited reliable estimates Mw. To address this, we calibrated coda envelopes at 16 broad-band seismic stations distributed across produce an Mw catalogue 100 events 2.13 that occurred since...
Abstract Stable single-station estimates of magnitude have been made using the 1-Hz Lg coda envelope regionally recorded nuclear explosions from Nevada Test Site (NTS). After empirical relations describing were found for each NTS-station path, single station magnitudes based on with precision in range 0.03 to 0.04 units, whereas third peak amplitude, rms and Pn amplitude had scatter order 0.15 0.2 generally five times larger than scatter. Despite high correlations, magnitude-yield residuals...
By using small-to-moderate earthquakes located within ∼200 km of San Francisco, we characterize the scaling ground motions for frequencies ranging between 0.25 and 20 Hz, obtaining results geometric spreading, Q ( f ), site parameters methods Mayeda et al. (2005) Malagnini (2004). The analysis show that, throughout Bay Area, average regional attenuation motion can be modeled with a bilinear spreading function 30-km crossover distance, coupled to an anelastic exp(− ϖfr / [capital greek beta]Q...
The determination of regional attenuation Q{sup -1} can depend upon the analysis method employed. discrepancies between methods are due to differing parameterizations (e.g., geometrical spreading rates), employed datasets choice path lengths and sources), methodologies themselves measurement in frequency or time domain). Here we apply five different a Northern California dataset. are: (1) coda normalization (CN), (2) two-station (TS), (3) reverse (RTS), (4) source-pair/receiver-pair (SPRP),...
The amount of energy radiated from an earthquake can be measured using recent methods based on coda signals and spectral ratios. Such are not altered by either site or directivity effects, with the advantage a greatly improved accuracy. Several studies sequences aforementioned measurements showed evidence breakdown in self‐similarity moment to relation. Radiated also used as gauge estimate average dynamic stress drop fault. Here we compute drop, infer coseismic friction heating resulting...