A5075258273- earthquake and tectonic studies
- Seismic Waves and Analysis
- High-pressure geophysics and materials
- Seismic Performance and Analysis
- Seismology and Earthquake Studies
- Earthquake Detection and Analysis
- Seismic Imaging and Inversion Techniques
- Geophysics and Sensor Technology
- Structural Health Monitoring Techniques
- Geological and Geochemical Analysis
- Landslides and related hazards
- Geophysical Methods and Applications
- Geotechnical Engineering and Underground Structures
- Atmospheric and Environmental Gas Dynamics
- Geophysics and Gravity Measurements
- Geophysical and Geoelectrical Methods
- Cold Fusion and Nuclear Reactions
- Laser-Plasma Interactions and Diagnostics
- Ionosphere and magnetosphere dynamics
- GNSS positioning and interference
- Economic, financial, and policy analysis
- Tunneling and Rock Mechanics
- Insurance and Financial Risk Management
- Disaster Management and Resilience
- Geotechnical and Geomechanical Engineering
United States Geological Survey
2007-2020
Earthquake Science Center
2019
Menlo School
1989-1997
Idaho National Laboratory
1985
Lamont-Doherty Earth Observatory
1978-1980
Columbia University
1978-1980
Stanford University
1975
abstract The far-field body wave radiation from a class of circular rupture models is investigated as function takeoff angle, velocity, and stopping behavior. In particular, the variation spectral shape, pulse energy flux over focal sphere quantified. These results provide two new methods for estimating source dimension, first through inversion characteristic frequency, second using rise time displacement shape. kinematic which has been constructed also allows direct estimate dynamic stress...
Abstract Averages of P- and S-wave radiation patterns over all azimuths various ranges takeoff angles (corresponding to observations at teleseismic, regional, near distances) have been computed for use in seismological applications requiring average coefficients. Various fault orientations averages the squared, absolute, logarithmic considered. Effective combining high-frequency direct surfacere-flected waves from shallow faults also derived used computation coefficients teleseismic...
Radiated energies from shallow earthquakes with magnitudes ≥5.8 that occurred between 1986 and 1991 are used to examine global patterns of energy release apparent stress. In contrast traditional methods which have relied upon empirical formulas, these computed through direct spectral analysis broadband seismic waveforms. Velocity‐squared spectra body waves integrated after they been corrected for effects arising depth phases, frequency‐dependent attenuation, focal mechanism. The least...
Fractal theory is applied in a quantitative analysis of the San Andreas fault (SAF) geometry. The method, which directly measures increase total length with decrease ruler size, gives fractal dimension D and scaling properties for chosen band 0.5–1000 km. A physical interpretation that it irregularity trace selected band. subdivided into six segments distinctive seismic behavior. “main” shows either maximum coseismic slip or creeping was analysis, three alternative branches examined SAF...
The energy flux contained in the P ‐wave groups ( + pP sP ) or S pS sS radiated by a shallow earthquake is modeled assuming that direct and depth phases adds incoherently. By defining generalized radiation patterns which incorporate this neutral interference, wave are analyzed as though they were comprised of single phase. Measurements corrected frequency domain for both body‐wave attenuation band recording. measurements then used to estimate seismic earthquake. This analysis applied digital...
abstract A statistically complete methodology for the analysis of SMA-1 data, including a direct inversion amplitude spectra, is developed and applied to records two small earthquakes ( M L = 1.5 in Attica 2.2 Blue Mountain Lake) obtained at epicentral distances ≈1 km. Using ray dependent corner frequency-radius relations, fault radii are determined be 80 ± 15 m 25 10 m. The stress drops vary by an order magnitude; Δσ 6 4 bars 85 60 bars. hydrofracture data estimate σ ¯ , average stress,...
Abstract Seventy-three digitally recorded body waves from nine multiply small earthquakes in Monticello, South Carolina, are analyzed to estimate the energy radiated P and S waves. Assuming Qα = Qβ 300, body-wave spectra corrected for attenuation frequency domain, velocity power integrated over flux. Focal mechanisms determined events by fitting observed displacement pulse areas used correct radiation patterns. Averaging results gives 27.3 ± 3.3 ratio of S-wave P-wave using 0.5 〈Fi〉 as a...
Abstract We derive an inversion scheme that fits the logarithms of seismic body-wave spectra to ω 2 source shapes conditioned by anelastic attenuation with a frequency-independent Q . The residuals from this fit are then projected onto set sources and sites, terms damped, estimate residual site response spectra. This two-part process is iterated until square residuals, summed over frequency for all recordings, minimized. absolute amplitudes determined fitting estimates amplification derived...
We consider how variations in fault frictional properties affect the phenomenology of earthquake faulting. In particular, we propose that lateral friction produce marked heterogeneity slip observed large earthquakes. model these using a rate‐ and state‐dependent law, where differentiate velocity‐weakening behavior into two fields: strong seismic field is very velocity weakening weak slightly weakening. Similarly, velocity‐strengthening compliant strengthening viscous strengthening. The...
Abstract The vertical components of the S wave trains recorded on Eastern Canadian Telemetered Network (ECTN) from 1980 through 1990 have been spectrally analyzed for source, site, and propagation characteristics. data set comprises some 1033 recordings 97 earthquakes whose magnitudes range M ≈ 3 to 6. epicentral distances 15 1000 km, with most at 200 800 km. contain phases S, SmS, Sn, Lg are sampled using windows that increase distance; acceleration spectra were 1.0 10 Hz. To separate...
A set of 16 large intraplate earthquakes are considered on the basis their tectonic settings, compressive focal mechanisms, and shallow depths as possible analogs for that may be anticipated to occur in northeastern North America. The range seismic moment from 5 × 1023 3 1026 dyne-cm include mainshocks largest aftershocks 1982 Miramichi, Canada, 1985 1988 Nahanni, Tennant Creek, Australia, earthquake sequences. teleseismic recordings these spectrally analyzed by correcting logarithmically...
Abstract The failure of an asperity, i.e., the dynamic rupture a small fault area with finite stress drop surrounded by broken or weak which has no but slips after asperity fails, is proposed as model for process subevent in composite earthquake. earthquake surrounding modeled model. resulting seismic moment proportional to and subevent, well radius earthaquake. By setting drops models equal subevents, can be sum set subevents cover scaling high- low-frequency radiation from earthquakes...
Abstract We derive a simple inversion of peak ground acceleration (PGA) or velocity (PGV) for rupture direction and then test this on the motions obtained from seven 3.5≤ M ≤4.1 earthquakes that occurred in two clusters November 2002 February 2003 near San Ramon, California. These were located orthogonal strike-slip faults so events share same approximate focal mechanism but not fault plane. Three exhibit strong directivity, other four relatively weak directivity. use residual PGAs PGVs six...
abstract A model for the far-field acceleration radiated by an incoherent rupture is constructed combining Madariaga's (1977) theory high-frequency radiation from crack models of faulting with a simple statistical source model. By extending results to pulses finite durations, peak pulse single stop or start tip shown depend on dynamic stress drop subevent, total change in velocity, and ratio subevent radius width. An approximated sample self-similar distribution coherent subevents. Assuming...
abstract Employing a new technique for the body-wave analysis of shallow-focus earthquakes, we have made preliminary St. Elias, Alaska earthquake February 28, 1979, using five long-period P and S waves recorded at three WWSSN stations Palisades, New York. Using well determined focal mechanism an average source depth ≈ 11 km, interference phases (i.e., pP sP, or sS) has been deconvolved from pulse shapes to obtain velocity displacement as they would appear if had occurred within infinite...
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 The M 6.2 Elmore Desert Ranch earthquake of 24 November 1987 was associated spatially and probably temporally with left-lateral surface rupture on many northeast-trending faults in near the Superstition Hills western Imperial Valley. Three curving discontinuous principal zones among these breaks extended northeastward from fault zone as far 9 km; maximum observed slip, 12.5 cm, northern three, fault, at a point epicenter. Twelve hours after earthquake, 6.6 occurred northwest end...
Abstract A suite of 111 strong-motion accelerograms for 14 aftershocks the Oroville, California, earthquake (ML = 5.7, 1 August 1975) that range in local magnitude (ML) from 2.8 to 5.2 has been analyzed obtain estimates seismic moment (Mo), source radius (ro), and stress drop (Δσ) addition focal parameters location, depth, fault-plane solution. This data set, which is unusually complete near-source (Δ ≲ 20 km) on-scale readings, allows greater precision calculation various measures...
The strong motion accelerograph recordings of the 24 January 1980 main shock and 27 aftershock Livermore Valley earthquake sequence are analyzed for systematic variations with azimuth or station location. variation peak accelerations epicentral is apparently reversed two events: larger to south, northwest. We eliminate site effects by forming ratio recorded at same station, after correcting distance. This analysis indicates that source directivity caused a total factor 10 in accelerations....
Five seismic estimates of stress release are compared for eight multiply recorded aftershocks the 1975 Oroville, California, earthquake. The dynamic drop, a rms and apparent provide stable which strongly correlated across data set. uncertainties these (the standard error mean divided by mean) approximately 15%. Estimates Brune drop uncorrelated with average static calculated from moments rupture geometries aftershocks, determined signal durations S waves. drops most drops, implying that...
Research Article| January 01, 1997 SEA96—A New Predictive Relation for Earthquake Ground Motions in Extensional Tectonic Regimes P. Spudich; Spudich U.S. Geological Survey Western Hazards Team Seismology Section Mail Stop 977 345 Middlefield Road Menlo Park, CA 94025 Search other works by this author on: GSW Google Scholar J.B. Fletcher; Fletcher M. Hellweg; Hellweg J. Boatwright; Boatwright C. Sullivan; Sullivan W.B. Joyner; Joyner T.C. Hanks; Hanks D.M. Boore; Boore A. McGarr; McGarr L.M....
We revise the spectral technique for estimating radiated energy from recordings of large earthquakes at regional distances (Δ 27.5 km source, we model geometrical spreading wavefield as r – γ where = 0.5 f ≤ 0.2 Hz and 0.7 ≥ 0.25 Hz. fit falloff with distance using a frequency-dependent attenuation Q 400( /1.5)0.6, 400 1.5 There is little directivity apparent in corrected velocity spectra: spectra observed to northwest along strike are amplified by factor 2.5 0.3 1.0 those southeast 1.6...
We have estimated the source parameters of 53 microearthquakes recorded in July 1983 which were aftershocks Miramichi, New Brunswick, earthquake that occurred on 9 January 1982. These events by local three-component digital seismographs at 400 sps/component from 2-Hz velocity transducers sited directly glacially scoured crystalline basement outcrop. Hypocentral distances are typically less than 5 km, and hypocenters seven seismograph stations established all lie essentially within boundaries...
A general technique is proposed for estimating rupture geometry from measurements of body wave durations, wherein the overall signal duration or a single pulse identified in all arrivals are inverted to estimate specific subevent, respectively. The complexity waveform determined by comparing most prominent waveform; this used ratio average velocity subevent velocity. shear waves radiated eight moderate (3.6≤ M L ≤4.9) multiply recorded aftershocks 1975 Oroville, California, earthquake...
Abstract The U.S. Geological Survey, Menlo Park, deployed and maintained a network of twelve digital instruments over the 2 weeks following 28 October 1983 Borah Peak, Idaho, earthquake. recorded 45 events with M ≧ 3.0, 6 ≦ 4.0. epicenters are located in narrow band which parallels trace surface fauiting up to Willow Creek summit; depths range from 5 16 km. In south, distribution hypocenters delineate plane dips southwest at 50°; north, dip steeply east. Composite focal mechanisms for three...