Earthquake aftershocks as Green's functions

Hartzell, Stephen H.

doi:10.1029/gl005i001p00001

Cited by 765 publications

(389 citation statements)

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“…To determine the source time functions (STFs), events at least one magnitude unit smaller than the mainshock, located within a few hundred meters of the mainshock, are used as empirical Green's functions [Hartzell, 1978;Frankel and Kanamori, 1983;Mori and Frankel, 1990;Mori, 1993]. These small aftershocks are considered as point sources in space and time such that their records consist of path and site effects only.…”

Section: Methods 41 Empirical Green's Function Methodsmentioning

confidence: 99%

Fine structure of the rupture zone of the April 26 and 27, 1997, Northridge aftershocks

Venkataraman¹,

Mori²,

Kanamori³

et al. 2000

J. Geophys. Res.

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Section: Methods 41 Empirical Green's Function Methodsmentioning

confidence: 99%

Fine structure of the rupture zone of the April 26 and 27, 1997, Northridge aftershocks

Venkataraman¹,

Mori²,

Kanamori³

et al. 2000

J. Geophys. Res.

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“…To extract information on the rupture kinematics from the observed seismograms, we applied an empirical Green's function (EGF)method to regional and teleseismic body and surface waves [Hartzell, 1978;Mueller, 1985 [Velasco et al, 1994a[Velasco et al, , 1994b[Velasco et al, , 1995[Velasco et al, , 1996. We used a 0.01% water level for our deconvolutions.…”

Section: Empirical Green's Function Analysismentioning

confidence: 99%

Broadband source modeling of the November 8, 1997, Tibet (M_w= 7.5) earthquake and its tectonic implications

Velasco¹,

Ammon²,

Beck³

2000

J. Geophys. Res.

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Abstract. We studied the source process of a large (M, = 7.9) intraplate earthquake that occurred on November 8, 1997, at 1002 UT in a remote region of northern Tibet. We used four distinct methods to investigate the broadband source process and thereby better understand the tectonic implications of this event. We relocated aftershocks using a master event technique and found that the distribution of aftershocks covers a region of 200 km in lateral extent. We also employed a surface wave spectral inversion technique to estimate the mainshock moment, depth, centroid location, and centroid time and utilized an empirical Green's function technique to extract rupture directivity information and a detailed source time function from observed seismograms. We also inverted body waves to estimate the moment release along the fault and the source time function. The 1997 earthquake ruptured a strike-slip fault that appears to be an extension or splay of the Kun Lun fault system. This fault is one of the most seismically active strike-slip faults within the Tibetan plateau and has had events with surface wave magnitudes of 6.1, 7.4, and 7.9 in this region since 1973. The rupture released most of the energy within the first 20 s and propagated bilaterally initially, with the later rupture propagating westward for 20-30 s. The absence of large aftershocks suggests that the earthquake efficiently released the stored strain. Comparing mainshock to the largest aftershock energy ratios for this event and other large strike-slip events shows that faulting within the plateau has the characteristics of weak faults (e.g., fracture zone faulting).

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“…The lower corner is related to the size of the finite fault, and the higher corner is related to the subfault size. This reflects the common assumption that large fault ruptures can be modeled by a series of smaller earthquakes (e.g., Hartzell, 1978).…”

Section: Introductionmentioning

confidence: 99%

Stochastic Modeling of California Ground Motions

Atkinson¹

2000

Bulletin of the Seismological Society of America

384

288

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Ground-motion relations are developed for California using a stochastic simulation method that exploits the equivalence between finite-fault models and a two-corner point-source model of the earthquake spectrum. First, stochastic simulations are generated for finite-fault ruptures, in order to define the average shape and amplitude level of the radiated spectrum at near-source distances as a function of earthquake size. The length and width of the fault plane are defined based on the moment magnitude of the earthquake and modeled with an array of subfaults. The radiation from each subfault is modeled as a Brune point source using the stochastic model approach; the subfault spectrum has a single-corner frequency. An earthquake rupture initiates at a randomly chosen subfault (hypocenter), and propagates in all directions along the fault plane. A subfault is triggered when rupture propagation reaches its center. Simulations are generated for an observation point by summing the subfault time series, appropriately lagged in time. Fourier spectra are computed for records simulated at many azimuths, placed at equidistant observation points around the fault. The mean Fourier spectrum for each magnitude, at a reference nearsource distance, is used to define the shape and amplitude levels of an equivalent point-source spectrum that mimics the salient finite-fault effects. The functional form for the equivalent point-source spectrum contains two corner frequencies.Stochastic point-source simulations, using the derived two-corner source spectrum, are then performed to predict peak-ground-motion parameters and response spectra for a wide range of magnitudes and distances, for generic California sites. The stochastic ground-motion relations, given in the Appendix for rock and soil sites, are in good agreement with the empirical strong-motion database for California; the average ratio of observed to simulated amplitudes is near unity over all frequencies from 0.2 to 12 Hz. The stochastic relations agree well with empirical regression equations (e.g., Abrahamson and Silva, 1997;Sadigh et al., 1997) in the magnitude-distance ranges well represented by the data, but are better constrained at large distances, due to the use of attenuation parameters based on regional seismographic data. The stochastic ground-motion relations provide a sound basis for estimation of ground motions for earthquakes of magnitude 4 through 8, at distances from 1 to 200 km.

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Earthquake aftershocks as Green's functions

Cited by 765 publications

References 7 publications

Fine structure of the rupture zone of the April 26 and 27, 1997, Northridge aftershocks

Fine structure of the rupture zone of the April 26 and 27, 1997, Northridge aftershocks

Broadband source modeling of the November 8, 1997, Tibet (M_w= 7.5) earthquake and its tectonic implications

Stochastic Modeling of California Ground Motions

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Earthquake aftershocks as Green's functions

Cited by 765 publications

References 7 publications

Fine structure of the rupture zone of the April 26 and 27, 1997, Northridge aftershocks

Fine structure of the rupture zone of the April 26 and 27, 1997, Northridge aftershocks

Broadband source modeling of the November 8, 1997, Tibet (Mw= 7.5) earthquake and its tectonic implications

Stochastic Modeling of California Ground Motions

Contact Info

Product

Resources

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Broadband source modeling of the November 8, 1997, Tibet (M_w= 7.5) earthquake and its tectonic implications