Finite‐Fault Bayesian Inversion of Teleseismic Body Waves

2017 ◽  
Vol 107 (3) ◽  
pp. 1526-1544
Author(s):  
Brandon S. Clayton ◽  
Stephen H. Hartzell ◽  
Morgan P. Moschetti ◽  
Sarah E. Minson
Keyword(s):  
Body Waves ◽  
Bayesian Inversion ◽  
Finite Fault

scholarly journals Development of an inversion method to extract information on fault geometry from teleseismic data

2019 ◽  
Vol 220 (2) ◽  
pp. 1055-1065 ◽  
Author(s):  
Kousuke Shimizu ◽  
Yuji Yagi ◽  
Ryo Okuwaki ◽  
Yukitoshi Fukahata
Keyword(s):  
Fault Plane ◽  
Slip Rate ◽  
Rate Function ◽  
Fault Slip ◽  
Body Waves ◽  
Fault System ◽  
Inversion Method ◽  
Fault Geometry ◽  
Finite Fault ◽  
Extract Information

SUMMARY Teleseismic waveforms contain information on fault slip evolution during an earthquake, as well as on the fault geometry. A linear finite-fault inversion method is a tool for solving the slip-rate function distribution under an assumption of fault geometry as a single or multiple-fault-plane model. An inappropriate assumption of fault geometry would tend to distort the solution due to Green’s function modelling errors. We developed a new inversion method to extract information on fault geometry along with the slip-rate function from observed teleseismic waveforms. In this method, as in most previous studies, we assumed a flat fault plane, but we allowed arbitrary directions of slip not necessarily parallel to the assumed fault plane. More precisely, the method represents fault slip on the assumed fault by the superposition of five basis components of potency-density tensor, which can express arbitrary fault slip that occurs underground. We tested the developed method by applying it to real teleseismic P waveforms of the MW 7.7 2013 Balochistan, Pakistan, earthquake, which is thought to have occurred along a curved fault system. The obtained spatiotemporal distribution of potency-density tensors showed that the focal mechanism at each source knot was dominated by a strike-slip component with successive strike angle rotation from 205° to 240° as the rupture propagated unilaterally towards the south-west from the epicentre. This result is consistent with Earth’s surface deformation observed in optical satellite images. The success of the developed method is attributable to the fact that teleseismic body waves are not very sensitive to the spatial location of fault slip, whereas they are very sensitive to the direction of fault slip. The method may be a powerful tool to extract information on fault geometry along with the slip-rate function without requiring detailed assumptions about fault geometry.

The Meckering earthquake of 14 October 1968: A possible downward propagating rupture

1987 ◽  
Vol 77 (5) ◽  
pp. 1558-1578
Author(s):  
Kristín S. Vogfjörd ◽  
Charles A. Langston
Keyword(s):  
Moment Tensor ◽  
Source Parameters ◽  
Time History ◽  
Vertical Displacement ◽  
Body Waves ◽  
Finite Fault ◽  
Short Period ◽  
Double Couple ◽  
The Moment ◽  
Fault Length

Abstract Average source parameters of the 1968 Meckering, Australia earthquake are obtained by the inversion of body waves. The objectives of the inversion are the elements of the moment tensor and the source-time history. An optimum source depth of 3 km is determined, but because of source complexity the point source assumption fails and the moment tensor obtained at that depth has a large nondouble-couple term, compensated linear vector dipole = 34 per cent. The source parameters of the major double-couple are: strike = 341°; dip = 37°; rake = 61°; and seismic moment = 8.2 ×1025 dyne-cm. The source-time function is of approximately 4 sec duration, with a long rise time and a sharp fall-off. The fault length is constrained on the surface by the observed surface break, and results from vertical displacement modeling suggest a width of approximately 10 km in the middle, assuming a dip of 37°. That restricts the entire faulted area to lie above 6 km depth. Two finite fault models for the earthquake are presented, with rupture initiating at a point (1) near the top of the fault and (2) at the bottom of the fault. Both models produce similar long-period synthetics, but based on the short-period waveforms, model 1 is favored. It is argued that such a rupture process is the most reasonable in this cold shield region.

scholarly journals Comparison of strong-motion spectra with teleseismic spectra for three magnitude 8 subduction-zone earthquakes

1990 ◽  
Vol 80 (4) ◽  
pp. 913-934
Author(s):  
Heidi Houston ◽  
Hiroo Kanamori
Keyword(s):  
Half Space ◽  
Site Response ◽  
Strong Motion ◽  
Body Waves ◽  
Reference Spectrum ◽  
Empirical Relations ◽  
Finite Fault ◽  
Simple Physical Model ◽  
Source Spectra ◽  
The Difference

Abstract We studied strong-motion spectra observed for three Mw 7.8 to 8.0 earthquakes (the 1985 Michoacán, Mexico; 1985 Valparaíso, Chile; and 1983 Akita-Oki, Japan earthquakes). We determined the decay of spectral amplitude with distance from the station, considering different measures of distance from a finite fault. We compared strong-motion spectra (Fourier acceleration spectra) observed for these three earthquakes with those estimated from the source spectrum determined from teleseismic P waves. We scaled the teleseismic source spectra to produce reference strong-motion spectra at periods from 1 to 10 sec using a simple physical model of far-field S body waves from a point source recorded at the surface of a homogeneous half-space. For all three earthquakes the reference spectral amplitudes at periods of 1 to 5 sec are about half the observed ones at distances of about 50 km. The difference increases as the distance increases. At distances of 200 to 300 km, the reference spectrum is about 1/10 of the observed one. The difference between the reference and the observed spectrum is attributed to the contribution of phases other than direct S waves and to site response. We applied corrections for the finiteness (spatial extent) of the source using a simple model of rupture propagation on a dipping two-dimensional fault. Including the source finiteness did not improve the estimate substantially at periods from 1 to 20 sec, but it modeled significant changes in the signal duration as a function of azimuth for the 1985 Michoacán earthquake. Our results can be used to establish empirical relations between the observed spectra and the half-space responses, depending on the distance and the site condition. If such empirical relations can be established, source spectra determined from teleseismic records may be used to estimate strong motions.

scholarly journals Bayesian inversion for finite fault earthquake source models – II: the 2011 great Tohoku-oki, Japan earthquake

2014 ◽  
Vol 198 (2) ◽  
pp. 922-940 ◽  
Author(s):  
S. E. Minson ◽  
M. Simons ◽  
J. L. Beck ◽  
F. Ortega ◽  
J. Jiang ◽  
...  
Keyword(s):  
Earthquake Source ◽  
Bayesian Inversion ◽  
Finite Fault ◽  
Source Models

scholarly journals The Mw 7.3 Papanoa, Mexico earthquake of April 18, 2014: Implications for recurrent M > 7 thrust earthquakes in western Guerrero

2017 ◽  
Vol 56 (1) ◽  
Author(s):  
Carlos Mendoza ◽  
María del Rosario Martínez López
Keyword(s):  
Waveform Inversion ◽  
Plate Boundary ◽  
Single Step ◽  
Body Waves ◽  
Slip Model ◽  
Coseismic Slip ◽  
Finite Fault ◽  
Rupture Model ◽  
Inversion Procedure ◽  
Mexico Earthquake

We apply a single-step, finite-fault waveform inversion procedure to derive a coseismic slip model for the large MW 7.3 Papanoa, Mexico earthquake of 18 April 2014 using broadband teleseismic body waves. Inversion of the P and SH ground-displacement waveforms yields a rupture model characterized by two principal sources of slip in the northwest portion of the Guerrero coast. The region is also the site of several M > 7 earthquakes in 1943, 1979 and 1985. A comparison of the 2014 slip model with ruptures observed for the 1979 and 1985 earthquakes suggests that the zones of high slip do not spatially coincide, despite similarities in the size and location of their aftershock areas. The zones of high coseismic slip are interpreted to represent asperity areas along the Cocos- North America plate boundary, and their limited spatial overlap from one event to another indicates that the rupture characteristics of recurring M > 7 thrust earthquakes in this portion of western Guerrero have not repeated in the last 70 years. The abutting nature of the asperities suggests that future large M > 7 earthquakes are likely to involve interplate patches between areas where large coseismic failure has been recently observed. Also, the observed asperities and their intervening regions may define locations where seismic failure may occur in future megathrust events. The results have important implications for the potential and recurrence of large M > 7 subduction earthquakes and the estimation of the strong ground motions expected from these events.

An adaptive Bayesian inversion for upper-mantle structure using surface waves and scattered body waves

2018 ◽  
Vol 214 (1) ◽  
pp. 232-253 ◽  
Author(s):  
Zachary Eilon ◽  
Karen M Fischer ◽  
Colleen A Dalton
Keyword(s):  
Surface Waves ◽  
Upper Mantle ◽  
Body Waves ◽  
Bayesian Inversion ◽  
Mantle Structure ◽  
Upper Mantle Structure

scholarly journals Source study of the 1906 San Francisco earthquake

1993 ◽  
Vol 83 (4) ◽  
pp. 981-1019 ◽  
Author(s):  
David J. Wald ◽  
Hiroo Kanamori ◽  
Donald V. Helmberger ◽  
Thomas H. Heaton
Keyword(s):  
San Francisco ◽  
Green's Functions ◽  
Green’S Functions ◽  
Body Waves ◽  
Source Analysis ◽  
Amplitude Ratios ◽  
Data Set ◽  
Loma Prieta Earthquake ◽  
Finite Fault ◽  
Loma Prieta

Abstract All quality teleseismic recordings of the great 1906 San Francisco earthquake archived in the 1908 Carnegie Report by the State Earthquake Investigation Commission were scanned and digitized. First order results were obtained by comparing complexity and amplitudes of teleseismic waveforms from the 1906 earthquake with well calibrated, similarly located, more recent earthquakes (1979 Coyote Lake, 1984 Morgan Hill, and 1989 Loma Prieta earthquakes) at nearly co-located modern stations. Peak amplitude ratios for calibration events indicated that a localized moment release of about 1 to 1.5 × 1027 dyne-cm was responsible for producing the peak the teleseismic body wave arrivals. At longer periods (50 to 80 sec), we found spectral amplitude ratios of the surface waves require a total moment release between 4 and 6 × 1027 dyne-cm for the 1906 earthquake, comparable to previous geodetic and surface wave estimates (Thatcher, 1975). We then made a more detailed source analysis using Morgan Hill S body waves as empirical Green's Functions in a finite fault subevent summation. The Morgan Hill earthquake was deemed most appropriate for this purpose as its mechanism is that of the 1906 earthquake in the central portion of the rupture. From forward and inverse empirical summations of Morgan Hill Green's functions, we obtained a good fit to the best quality teleseismic waveforms with a relatively simple source model having two regions of localized strong radiation separated spatially by about 110 km. Assuming the 1906 epicenter determined by Bolt (1968), this corresponds with a large asperity (on the order of the Loma Prieta earthquake) in the Golden Gate/San Francisco region and one about three times larger located northwest along strike between Point Reyes and Fort Ross. This model implies that much of the 1906 rupture zone may have occurred with relatively little 10 to 20 sec radiation. Consideration of the amplitude and frequency content of the 1906 teleseismic data allowed us to estimate the scale length of the largest asperity to be less than about 40 km. With rough constraints on the largest asperity (size and magnitude) we produced a suite of estimated synthetic ground velocities assuming a slip distribution similar to that of the Loma Prieta earthquake but with three times as much slip. For purposes of comparison with the recent, abundant Loma Prieta strong motion data set, we “moved” the largest 1906 asperity into Loma Prieta region. Peak ground velocity amplitudes are substantially greater than those recorded during the Loma Prieta earthquake, and are comparable to those predicted by the attenuation relationship of Joyner and Boore (1988) for a magnitude MW = 7.7 earthquake.

scholarly journals Bayesian inversion for finite fault earthquake source models I—theory and algorithm

2013 ◽  
Vol 194 (3) ◽  
pp. 1701-1726 ◽  
Author(s):  
S. E. Minson ◽  
M. Simons ◽  
J. L. Beck
Keyword(s):  
Earthquake Source ◽  
Bayesian Inversion ◽  
Finite Fault ◽  
Source Models
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