Systematic deficiency of aftershocks in areas of high coseismic slip for large subduction zone earthquakes

Wetzler, Nadav; Lay, Thorne; Brodsky, E. E.; Kanamori, Hiroo

doi:10.1126/sciadv.aao3225

Cited by 74 publications

(84 citation statements)

References 37 publications

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“…Besides the 2016 sequence, Trugman and Shearer () observed that the stress drops of these mainshocks are quite large, which is consistent with the generally large mainshock‐aftershock distances of all examined aftershock sequences (Figure ). Similar observations for global megathrust earthquakes were analyzed by Wetzler et al ().…”

Section: Resultssupporting

confidence: 83%

Diverse Volumetric Faulting Patterns in the San Jacinto Fault Zone

2018

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We examine locations, magnitudes, and faulting types of post‐2000 earthquakes in the trifurcation area of San Jacinto fault zone to clarify basic aspects of failure processes in the area. Most M ≥ 3.5 events have strike‐slip mechanisms, occur within 1 km of the main faults (Clark, Buck Ridge, and Coyote Creek), and have hypocenter depths of 10–13 km. In contrast, many smaller events have normal source mechanisms and hypocenters in intrafault areas deeper than 13 km. Additional small events with hypocenter depth <13 km occur in off‐fault regions and have complex geometries including lineations normal to the main faults. Five moderate earthquakes with M 4.7–5.4 have high aftershock rates (~150 M ≥ 1.5 events within 1 day from the mainshock). To obtain more details on aftershock sequences of these earthquakes, we detect and locate additional events with the matched filter method. There are almost no aftershocks within 1 km from the mainshocks, consistent with large mainshock stress drops and low residual stress. The five aftershock sequences have almost no spatial overlap. While the mainshocks are on the main faults, most aftershocks are located in intrafault and off‐fault regions. Their locations and spatial distribution reflect the mainshock rupture directions, and many also follow structures normal to the main faults. The significant diversity of observed features highlights the essential volumetric character of failure patterns in the area. The increasing rate of moderate events, productive aftershock sequences, and large inferred stress drops may reflect processes near the end of a large earthquake cycle.

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Section: Resultssupporting

confidence: 83%

Diverse Volumetric Faulting Patterns in the San Jacinto Fault Zone

2018

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“…Almost all the early aftershocks (within 3 days) of the Guthrie event are located at the periphery of the inferred rupture model (Figure ), indicating a possible causal dynamic and/or static triggering effects. The absence of early aftershocks in our modeled rupture area suggests an anticorrelation of aftershock productivity with the slip distribution, which was also observed for earthquakes in various tectonic settings (e.g., Mendoza & Hartzell, ; Ross et al, ; Wetzler et al, ; Wu et al, ). The framework that combines stress transfer and source directivity (e.g., Convertito et al, ) may be further improved by incorporating pore pressure increase and poroelastic stress changes due to injection to better explain triggering mechanisms of induced earthquakes.…”

Section: Discussionsupporting

confidence: 78%

Source Complexity of the 2015 Mw 4.0 Guthrie, Oklahoma Earthquake

Chen

Abercrombie

2019

Geophysical Research Letters

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We demonstrate the complex source process of a potentially induced Mw 4.0 earthquake near Guthrie, Oklahoma. Relative source time functions (RSTFs), retrieved using a time domain empirical Green's function (EGF) deconvolution method, show clear evidence of rupture complexity with the presence of multiple pulses and systematic azimuthal variations. Directivity analysis reveals a well‐defined rupture propagation at ~120° toward the southeast. Detailed modeling of the RSTFs results in a four‐subevent model spanning ~1 s in time and ~1.5 km in space, in which the earthquake ruptured four successive slip episodes unilaterally to the southeast. Multiple EGF spectral ratio analysis also shows significant complexity as evidenced by azimuth‐dependent deviations from the omega‐square (Brune) model. The observations of the concentration of early aftershocks at the periphery of the inferred rupture model along the rupture direction and amplified ground motions at stations to the southeast can both be well explained by the directivity effect.

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“…Few aftershocks occurred below 8 km depth, and no aftershocks surround the areas of higher slip on the deeper parts of the fault. Aftershock distribution from the Pawnee earthquake differs from observations from other earthquakes, for which most aftershocks occur outside of the regions of high slip (e.g., Mendoza & Hartzell, 1988;Wetzler et al, 2018).…”

Section: Finite-fault Rupture Modelmentioning

confidence: 67%

Rupture Model of the M5.8 Pawnee, Oklahoma, Earthquake From Regional and Teleseismic Waveforms

Moschetti

Hartzell

Herrmann

2019

Geophysical Research Letters

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The 2016 M5.8 Pawnee, Oklahoma, earthquake is the largest earthquake to have been induced by wastewater disposal. We infer the coseismic slip history from analysis of apparent source time functions and inversion of regional and teleseismic P waveforms, using aftershocks as empirical Green's functions. The earthquake nucleated on the shallow part of the fault, initially rupturing toward the surface, followed shortly thereafter by slip deeper on the fault. Deeper slip occurred below the aftershocks and at greater depths than most induced seismicity in the region, suggesting that small‐ to moderate‐sized earthquakes may not occur on deeper parts of faults in Oklahoma because they are further from failure than shallower fault sections. Comparisons with models of pore pressure perturbations further suggest that the earthquake may have initiated within a region of higher pore pressure perturbation but was not confined to this zone. These observations inform source physics and understanding of maximum magnitudes.

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Systematic deficiency of aftershocks in areas of high coseismic slip for large subduction zone earthquakes

Abstract: Aftershock deficiency in large-slip zones of major subduction zone earthquake ruptures indicates below-critical shear stress.

Cited by 74 publications

References 37 publications

Diverse Volumetric Faulting Patterns in the San Jacinto Fault Zone

Diverse Volumetric Faulting Patterns in the San Jacinto Fault Zone

Source Complexity of the 2015 Mw 4.0 Guthrie, Oklahoma Earthquake

Rupture Model of the M5.8 Pawnee, Oklahoma, Earthquake From Regional and Teleseismic Waveforms

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