John Boatwright

United States Geological Survey

Author Statistics

Papers

Citation

H-Index

i-10 index

Research Trends

Author Order

Document Type

Co-Authors

George L. Choy

United States Geological Survey

J. B. Fletcher

United States Geological Survey

Linda C. Seekins

United States Geological Survey

David M. Boore

United States Geological Survey

Howard Bundock

United States Geological Survey

A. Baltay

United States Geological Survey

M. Cocco

Istituto Nazionale di Geofisica e Vulcanologia

Lawrence M. Baker

United States Geological Survey

Paul Spudich

United States Geological Survey

R. D. Catchings

United States Geological Survey

Cooperative Institutions

United States Geological Survey

104

Menlo School

Earthquake Science Center

United States Department of the Interior

University of California, Berkeley

California Institute of Technology

Pacific Island Ecosystems Research Center

Stanford University

Denver Federal Center

California Geological Survey

Author Statistics

Papers

Citation

H-Index

i-10 index

Research Field

Regional Estimates of Radiated Seismic Energy

Bulletin of the Seismological Society of America (2002)

John Boatwright

We revise the spectral technique for estimating radiated energy from recordings of large earthquakes at regional distances (Δ 27.5 km from the source, we model the geometrical spreading of the regional wavefield as r – γ where γ = 0.5 for f ≤ 0.2 Hz and γ = 0.7 for f ≥ 0.25 Hz. We fit the spectral falloff with distance using a frequency-dependent attenuation Q = 400( f /1.5)0.6, where Q = 400 for f ≤ 1.5 Hz. There is little directivity apparent in the corrected velocity spectra: the velocity spectra observed to the northwest along strike are amplified by a factor of 2.5 from 0.3 to 1.0 Hz and those to the southeast are amplified by a factor of 1.6 from 0.3 to 0.7 Hz. We group the stations in NEHRP site classes, using average 1-D velocity structures to estimate site amplification as a function of frequency and assuming 0.40 ≤ κ ≤ 0.55 sec for the near-surface attenuation. We increase the amplification of the soft-soil sites from 0.1 to 1.0 Hz by a factor that reaches 1.7 at 0.3 Hz because they are more strongly amplified than the NEHRP-D velocity structure predicts. We combine the 65 single-station estimates of radiated energy using an equal-azimuth weighting scheme that compensates for station distribution and incorporates the observed directivity, yielding a regional estimate of E s = 3.4 ± 0.7 × 1022 dyne cm. This regional estimate of radiated energy corresponds closely to the teleseismic estimate of E s = 3.2 × 1022 dyne cm.

Seismic energy

10.1785/0120000932

Cite

Citations (82)

A comparison of coda and S-wave spectral ratios as estimates of site response in the southern San Francisco Bay area

Bulletin of the Seismological Society of America (1994)

Lucia Margheriti Leif Wennerberg John Boatwright

Abstract We calculate spectral ratios for S waves and codas to evaluate the amplification of 14 sites in the southern San Francisco Bay area relative to a nearby bedrock site in the Coyote Hills. Our data are seismograms written by Loma Prieta aftershocks: the epicentral distances and azimuths to the stations are effectively the same. All the sites in the study are amplified with respect to the reference site at frequencies from 0.5 to 7 Hz. The shapes of the S -wave and coda spectral ratios are similar, but the coda ratios are greater than the S -wave ratios by as much as a factor of 4. The difference is larger for sites on alluvial and bay mud deposits, particularly at frequencies around 1 Hz, suggesting the presence of waves trapped in the alluvial basin. In general, the length of the analysis window affects the S -wave spectral ratios for alluvial sites. Longer windows give ratios similar to coda ratios, apparently because these windows include more of the phases that contribute to the coda. We classify the sites according to their geological characteristics and surficial shear-wave velocities. For the S -wave ratios, the differences between the classes showed no systematic trend; the softest and hardest soil classes we consider have practically identical S -wave amplifications. The average coda ratios for the site classes clearly increase as the soil classes include slower and “softer” materials. After correction for differences in reference sites, the coda amplifications are very similar to the relative amplifications for these site classes estimated by Borcherdt and Glassmoyer (1992) from the strong-motion recordings of the 1989 Loma Prieta earthquake.

Coda

Seismogram

Bedrock

S-wave

Bay mud

10.1785/bssa0840061815

Cite

Citations (49)

The effect of rupture complexity on estimates of source size

Journal of Geophysical Research Atmospheres (1984)

John Boatwright

A general technique is proposed for estimating rupture geometry from measurements of body wave durations, wherein measurements of the overall signal duration or the duration of a single pulse identified in all of the arrivals are inverted to estimate the geometry of the overall rupture or of a specific subevent, respectively. The complexity of a waveform is determined by comparing the overall signal duration to the duration of the most prominent pulse in the waveform; this complexity is used to estimate the ratio of the average rupture velocity to the subevent rupture velocity. The shear waves radiated by eight moderate (3.6≤ M L ≤4.9) multiply recorded aftershocks of the 1975 Oroville, California, earthquake are analyzed using measurements of the corner frequency, the characteristic frequency, the pulse duration, and the signal duration. Comparison of these four different estimates of source size indicates that the corner frequency and the characteristic frequency are more sensitive to the dominant subevent size than to the overall event size. The difference between the estimates of source size determined from the signal duration measurements and the spectral measurements increases as the rupture complexity increases.

Pulse duration

SIGNAL (programming language)

10.1029/jb089ib02p01132

Cite

Citations (71)

Quasi-dynamic models of simple earthquakes: Application to an aftershock of the 1975 Oroville, California, earthquake

Bulletin of the Seismological Society of America (1981)

John Boatwright

A class of kinematic rupture models for simple earthquakes is proposed; these models incorporate results from both theoretical and numerical solutions to the mixed boundary value problem of a three-dimensional frictional rupture. The analytic form for the slip velocity is divided into two phases: the rupture growth, during which the slip distribution is “self-similar” (Kostrov, 1964); and the healing, during which the slip velocity decreases monotonically to zero. The arrival of a P -wave stopping phase, propagating into the interior of the rupture area from the fault perimeter, initiates the healing. The duration of healing may be varied to produce a gradual or abrupt stopping of the rupture, which permits modeling a wide range of high-frequency spectral behavior. These models are used to generate synthetics which are fit to the velocity and the velocity-squared pulse shapes obtained from strong motion accelerograms of the 0103 aftershock of the 1975 Oroville, California, earthquake. The aftershock ( ML = 4.6) has a moment of 1.8 × 1023 dyne-cm and a total radiated energy of 2.7 × 1019 dyne-cm. The fitted source model propagates updip with a rupture velocity of 0.85 β and a dynamic stress drop of 210 bars. The arrival times of five “stopping phases”, correlated across the suite of accelerograms, are used to determine the relative locations of the hypocenter and five stopping events. The description of rupture determined from these stopping events both corroborates the source model obtained from the waveform modeling and establishes an important counterpoint to the model by providing a dynamic interpretation of the unmodeled complexity of the waveforms.

Hypocenter

10.1785/bssa0710010069

Cite

Citations (61)

The 2007 M5.4 Alum Rock, California, earthquake: Implications for future earthquakes on the central and southern Calaveras Fault

Journal of Geophysical Research Atmospheres (2010)

David H. Oppenheimer W. H. Bakun Tom Parsons Robert W. Simpson John Boatwright

The similarity of seismograms recorded by two seismic stations demonstrate that the 31 October 2007 moment magnitude M 5.4 Alum Rock earthquake is a repeat of a 1955 M L 5.5 earthquake. Both occurred on Oppenheimer et al.'s (1990) Zone V “stuck patch” on the central Calaveras fault, providing new support for their model of Calaveras fault earthquake activity. We suggest that Zone V fails only in a family of recurring M ∼ 5.4–5.5 earthquakes. The 1955 and 2007 earthquakes are the penultimate and ultimate Zone V events. Earthquakes in 1891 and 1864 are possible earlier Zone V events. The next Zone V event is not expected in the next few decades, assuming a time‐dependent recurrence model: the mean forecast date is 2064 (2035–2104, 95% confidence range). We further suggest that Zones I, II, III, and IV fail in recurring M ∼ 5.1–5.3, M ∼ 5.6–5.8, M ∼ 6.1–6.3, and M ∼ 4.9–5.0 earthquakes, respectively. If our earthquake recurrence model is correct, the next Zone I event is overdue and could occur anytime, and M 5–6 earthquakes should not occur on Zones II, III, and IV before 2014, 2012, and 2026, respectively. We cannot rule out the possibility that Zone VI, which lies at the southern end of the Mission Seismic Trend, where the southern Hayward and central Calaveras faults appear to connect at depth, fails aseismically or in large events on the southern Hayward fault, such as last occurred in 1868, or in large events on the adjoining northern Calaveras fault segment.

Seismogram

Seismic zone

Moment magnitude scale

Seismic moment

Earthquake prediction

10.1029/2009jb006683

Cite

Citations (11)

Acceleration spectra for subduction zone earthquakes

Journal of Geophysical Research Atmospheres (1989)

John Boatwright George L. Choy

We estimate the source spectra of shallow earthquakes from digital recordings of teleseismic P wave groups, that is, P + p P + s P , by making frequency dependent corrections for the attenuation and for the interference of the free surface. The correction for the interference of the free surface assumes that the earthquake radiates energy from a range of depths. We apply this spectral analysis to a set of 12 subduction zone earthquakes which range in size from M S = 6.2 to 8.1, obtaining corrected P wave acceleration spectra on the frequency band from 0.01 to 2.0 Hz. Seismic moment estimates from surface waves and normal modes are used to extend these P wave spectra to the frequency band from 0.001 to 0.01 Hz. The acceleration spectra of moderate subduction zone earthquakes, that is, earthquakes whose seismic moments are less than 10 27 dyn cm, exhibit ω‐square or Brune‐type spectra, while the acceleration spectra of large subduction zone earthquakes, that is, earthquakes whose seismic moments are greater than 10 27 dyn cm, exhibit intermediate slopes where ü(ω) ∝ ω 5/4 for frequencies from 0.005 to 0.05 Hz. For this set of earthquakes, spectral shape appears to be a discontinuous function of seismic moment. Using reasonable assumptions for the phase characteristics, we transform the spectral shape observed for large earthquakes into the time domain to fit Ekström's (1987) moment rate functions for the M S = 8.1 Michoacan earthquake of September 19, 1985, and the M S = 7.6 Michoacan aftershock of September 21, 1985.

Seismic moment

Moment magnitude scale

Spectral acceleration

10.1029/jb094ib11p15541

Cite

Citations (33)

Chapter A. The Loma Prieta, California, Earthquake of October 17, 1989 - Main shock characteristics

USGS professional paper (1996)

Paul Spudich Gregory C. Beroza George L. Choy John Boatwright Stephen Hartzell

10.3133/pp1550a

Cite

Citations (13)

The Seismic Radiation from a 3-D Dynamic Model of a Complex Rupture Process. Part I: Confined Ruptures

Geophysical monograph (2011)

John Boatwright H. R. Quin

We have analyzed a class of rupture models with spontaneous rupture growth and spatially variable stress and strength using a computationally rapid solution of the 3-D boundary integral equation for dynamic rupture on a planar fault. The distributions of initial stress and strength are assumed to be self-similar; their spectral variation is assumed to be inversely proportional to wavenumber raised to three-halves power. The initial stress and strength are weakly correlated. The ruptures are confined by a fixed (i.e., high-strength) rupture perimeter. This unphysical confinement allows both an optimal use of the limited computational duration of the model and direct comparison with results obtained from kinematic models. The significant parameters of the dynamic models are the rms normalized strength, 〈S〉, and the relative variation of the initial stress and strength. The average rupture velocity is controlled by the normalized strength; to distinguish ruptures with transonic and subsonic rupture velocities, we consider 〈S〉 = 1.0 and 1.5, respectively. The complexity of the rupture process is proportional to the variation of the initial stress and strength. In general, the complex ruptures exhibit significant variations of rupture velocity, and the rupture fronts are irregular in shape. The body-waves radiated by these models are calculated from the far-field terms of the Green's function. The radiated energy flux is calculated by integrating the velocity power spectrum. These integrals and the body-wave acceleration spectra are averaged over the focal sphere. For these confined ruptures, the radiation efficiency and the rms S-wave spectrum depend on the average rupture velocity but do not depend on the complexity of the rupture process. As the ruptures become more complex, the amplitude of the stopping phases decreases while the number of phases radiated from the interior of the rupture area increases. The ruptures with transonic rupture velocities radiate more energy than the subsonic ruptures.

Stress field

10.1029/gm037p0097

Cite

Citations (34)

Broadband analysis of the extended foreshock sequence of the Miyagi-Oki earthquake of 12 June 1978

Bulletin of the Seismological Society of America (1982)

George L. Choy John Boatwright

abstract The Miyagi-Oki earthquake of 12 June 1978, a large (Ms 7.8) interplate thrust event, occurred in a region which had not experienced earthquakes of magnitude greater than 7 since 1938. A sequence of four moderate-sized (5.4 < mb < 6.1) earthquakes encircled the rupture zone of the Miyagi-Oki earthquake over a period of 2 yr before the main shock. Broadband displacement and velocity records of body waves recorded digitally by stations of the Global Digital Seismograph Network are analyzed to determine the static and dynamic characteristics of the sequence. These characteristics include moment, radiated energy, dynamic and static stress drop, and apparent stress. Inversions of duration measurements made on the velocity waveforms permit quantifying the complexity of an event as well as constraining its rupture geometry. Intervals of 7 to 8 months separated the first three events; the main shock occurred 4 months after the third event. The rupture process of the third event was relatively complex; the event also had a substantially higher dynamic stress drop (175 bars) than did the stress drops of the first two events (9 and 10 bars, respectively). These observations suggest that the third event was an interme-diate-term precursor to the main shock. The fourth event, a short-term precursor to the main shock, occurred about 8 min before the main shock. Its dynamic stress drop (20 bars) was lower than that of the third event but higher than that of the first two events.

Seismometer

Dynamic stress

10.1785/bssa07206a2017

Cite

Citations (17)

Comments on “energy radiation from a spherically symmetric homogeneous source” by J. W. Rudnicki

Bulletin of the Seismological Society of America (1984)

John Boatwright

Letter| August 01, 1984 Comments on “energy radiation from a spherically symmetric homogeneous source” by J. W. Rudnicki John Boatwright John Boatwright U.S. Geological Survey345 Middlefield RoadMenlo Park, California 94025 Search for other works by this author on: GSW Google Scholar Author and Article Information John Boatwright U.S. Geological Survey345 Middlefield RoadMenlo Park, California 94025 Publisher: Seismological Society of America Received: 29 Apr 1983 First Online: 03 Mar 2017 Online Issn: 1943-3573 Print Issn: 0037-1106 Copyright © 1984, by the Seismological Society of America Bulletin of the Seismological Society of America (1984) 74 (4): 1483–1486. https://doi.org/10.1785/BSSA0740041483 Article history Received: 29 Apr 1983 First Online: 03 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation John Boatwright; Comments on “energy radiation from a spherically symmetric homogeneous source” by J. W. Rudnicki. Bulletin of the Seismological Society of America 1984;; 74 (4): 1483–1486. doi: https://doi.org/10.1785/BSSA0740041483 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyBulletin of the Seismological Society of America Search Advanced Search This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Icon

10.1785/bssa0740041483

Cite

Citations (1)