Ground Motion Prediction Equations in the San Jacinto Fault Zone: Significant Effects of Rupture Directivity and Fault Zone Amplification

Kurzon, Ittai; Vernon, F. L.; Ben‐Zion, Yehuda; Atkinson, Gail M.

doi:10.1007/s00024-014-0855-2

Cited by 78 publications

(73 citation statements)

References 48 publications

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“…Weertman 1980;Ben-Zion & Andrews 1998;Ampuero & Ben-Zion 2008;Brietzke et al 2009) suggest that earthquakes in the area tend to propagate to the northwest. This is consistent with observed directivities of small to moderate events on the section southeast of the array (Kurzon et al 2014;, along-strike Table 2. Upper and lower bounds placed on, and incremental change allowed in, the parameter space during inversions of events tw1 and tw2 (Figs 11 and 12).…”

Section: Discussionsupporting

confidence: 90%

Internal structure of the San Jacinto fault zone at Blackburn Saddle from seismic data of a linear array

Ben‐Zion

Ross

et al. 2017

Geophysical Journal International

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S U M M A R YLocal and teleseismic earthquake waveforms recorded by a 180-m-long linear array (BB) with seven seismometers crossing the Clark fault of the San Jacinto fault zone northwest of Anza are used to image a deep bimaterial interface and core damage structure of the fault. Delay times of P waves across the array indicate an increase in slowness from the southwest most (BB01) to the northeast most (BB07) station. Automatic algorithms combined with visual inspection and additional analyses are used to identify local events generating fault zone head and trapped waves. The observed fault zone head waves imply that the Clark fault in the area is a sharp bimaterial interface, with lower seismic velocity on the southwest side. The moveout between the head and direct P arrivals for events within ∼40 km epicentral distance indicates an average velocity contrast across the fault over that section and the top 20 km of 3.2 per cent. A constant moveout for events beyond ∼40 km to the southeast is due to off-fault locations of these events or because the imaged deep bimaterial interface is discontinuous or ends at that distance. The lack of head waves from events beyond ∼20 km to the northwest is associated with structural complexity near the Hemet stepover. Events located in a broad region generate fault zone trapped waves at stations BB04-BB07. Waveform inversions indicate that the most likely parameters of the trapping structure are width of ∼200 m, S velocity reduction of 30-40 per cent with respect to the bounding blocks, Q value of 10-20 and depth of ∼3.5 km. The trapping structure and zone with largest slowness are on the northeast side of the fault. The observed sense of velocity contrast and asymmetric damage across the fault suggest preferred rupture direction of earthquakes to the northwest. This inference is consistent with results of other geological and seismological studies.

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Section: Discussionsupporting

confidence: 90%

Internal structure of the San Jacinto fault zone at Blackburn Saddle from seismic data of a linear array

Ben‐Zion

Ross

et al. 2017

Geophysical Journal International

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“…With the aim of testing the lower magnitude limit of our method in this section, we select the 2013 March 11 M w 4.7 earthquake which occurred in the SJFT region of southern California, for which a strong northwestward directivity has been reported in previous studies (Kurzon et al 2014;Ross & Ben-Zion 2016). As the Southern California Seismic Network is dense, we only use stations within an epicentral distance of 100 km for analysis (Fig.…”

Section: W 47 Sjft Earthquake In the Southern Californiamentioning

confidence: 99%

“…As unilateral rupture occurs, seismic waves radiated in the direction of rupture could be greatly amplified, and even moderate magnitude earthquakes can sometimes cause serious damage (Huang et al 2011;Kanamori et al 2016). Knowing the directivity of earthquakes is therefore important for ground shaking prediction and in turn helps with hazard mitigation (Somerville et al 1997;Spudich & Chiou 2008;Kurzon et al 2014). Moreover, directivity can also be used to discriminate which nodal plane corresponds to the actual fault plane (Mori & Hartzell 1990;Warren & Shearer 2006;Frez et al 2010).…”

Section: Introductionmentioning

confidence: 99%

“…Although these methods provide a spatiotemporal history of the rupture process, their application is mainly restricted to large earthquakes. More commonly, directivity for small-to-moderate earthquakes is estimated based on differences in source duration (Velasco et al 1994;Tan & Helmberger 2010) or peak ground amplitude (Boatwright 2007;Convertito et al 2012;Kurzon et al 2014) observed between stations in the time domain, or differences in spectral ratios (Wang & Rubin 2011;Ross & BenZion 2016) or corner frequencies (Kane et al 2013) in the frequency domain. These studies convert observations of a single source parameter at each station to estimate directivity and therefore rely on a good azimuthal coverage of stations to resolve directivity since information at each station has been reduced to a single parameter.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Toward automated directivity estimates in earthquake moment tensor inversion

Huang

Aso

Tsai

2017

Geophysical Journal International

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S U M M A R YRapid estimates of earthquake rupture properties are useful for both scientific characterization of earthquakes and emergency response to earthquake hazards. Rupture directivity is a particularly important property to constrain since seismic waves radiated in the direction of rupture can be greatly amplified, and even moderate magnitude earthquakes can sometimes cause serious damage. Knowing the directivity of earthquakes is important for ground shaking prediction and hazard mitigation, and is also useful for discriminating which nodal plane corresponds to the actual fault plane particularly when the event lacks aftershocks or outcropped fault traces. Here, we propose a 3-D multiple-time-window directivity inversion method through direct waveform fitting, with source time functions stretched for each station according to a given directivity. By grid searching for the directivity vector in 3-D space, this method determines not only horizontal but vertical directivity components, provides uncertainty estimates, and has the potential to be automated in real time. Synthetic tests show that the method is stable with respect to noise, picking errors, and site amplification, and is less sensitive to station coverage than other methods. Horizontal directivity can be properly recovered with a minimum azimuthal station coverage of 180 • , whereas vertical directivity requires better coverage to resolve. We apply the new method to the M w 6.0 Nantou, Taiwan earthquake, M w 7.0 Kumamoto, Japan earthquake, and M w 4.7 San Jacinto fault trifurcation (SJFT) earthquake in southern California. For the Nantou earthquake, we corroborate previous findings that the earthquake occurred on a shallow east-dipping fault plane rather than a west-dipping one. For the Kumamoto and SJFT earthquakes, the directivity results show good agreement with previous studies and demonstrate that the method captures the general rupture characteristics of large earthquakes involving multiple fault ruptures and applies to earthquakes with magnitudes as small as M w 4.7.

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“…For example, waves reflected from and propagated along the interfaces between the LVZ and intact rocks may strongly modulate the rupture propagation, including oscillations of rupture speed and generation of multiple slip pulses . In addition, the LVZ may result in amplification of ground motion near faults (e.g., Wu et al 2009;Avallone et al 2014;Kurzon et al 2014) and may influence long-term deformation processes in the crust (e.g., Finzi et al 2009;. Moreover, cracks in the damage zone may store and transport fluids that play an important role on fault zone strength (Eberhart-Phillips et al 1995).…”

Section: Fz Properties and Their Effectsmentioning

confidence: 99%

Recent advances in imaging crustal fault zones: a review

Yang

2015

Earthq Sci

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Crustal faults usually have a fault core and surrounding regions of brittle damage, forming a low-velocity zone (LVZ) in the immediate vicinity of the main slip interface. The LVZ may amplify ground motion, influence rupture propagation, and hold important information of earthquake physics. A number of geophysical and geodetic methods have been developed to derive high-resolution structure of the LVZ. Here, I review a few recent approaches, including ambient noise cross-correlation on dense across-fault arrays and GPS recordings of fault-zone trapped waves. Despite the past efforts, many questions concerning the LVZ structure remain unclear, such as the depth extent of the LVZ. High-quality data from larger and denser arrays and new seismic imaging technique using larger portion of recorded waveforms, which are currently under active development, may be able to better resolve the LVZ structure. In addition, effects of the alongstrike segmentation and gradational velocity changes across the boundaries between the LVZ and the host rock on rupture propagation should be investigated by conducting comprehensive numerical experiments. Furthermore, high-quality active sources such as recently developed large-volume airgun arrays provide a powerful tool to continuously monitor temporal changes of fault-zone properties, and thus can advance our understanding of fault zone evolution.

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Ground Motion Prediction Equations in the San Jacinto Fault Zone: Significant Effects of Rupture Directivity and Fault Zone Amplification

Cited by 78 publications

References 48 publications

Internal structure of the San Jacinto fault zone at Blackburn Saddle from seismic data of a linear array

Internal structure of the San Jacinto fault zone at Blackburn Saddle from seismic data of a linear array

Toward automated directivity estimates in earthquake moment tensor inversion

Recent advances in imaging crustal fault zones: a review

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