Why Do Aftershocks Occur Within the Rupture Area of a Large Earthquake?

Yabe, Suguru; Ide, Satoshi

doi:10.1029/2018gl077843

Cited by 21 publications

(8 citation statements)

References 47 publications

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“…asperities' of the 1942, 1958 and ruptures are separated by weak zones that typically behave aseismically, but can slip abruptly when driven by failure of neighbouring asperities -this mechanism was proposed to explain the coordinated rupture of all three asperities in a M w 8.8 earthquake in 1906. Indeed, frictional properties may vary during the course of the earthquake cycle, and patches that are conditionally stable may participate in both coseismic and aseismic slip phases Yabe and Ide [2018]. modeled a frictionally heterogeneous fault system and their quasi-dynamic numerical simulation results were able to reproduce afterslip and aftershocks occurring around and within the mainshock rupture zone.…”

mentioning

confidence: 99%

Imaging rapid early afterslip of the 2016 Pedernales earthquake, Ecuador

Tsang

Vergnolle

Twardzik

et al. 2019

Earth and Planetary Science Letters

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High-Rate (HR) GPS time series following the 2016 M w 7.8 Pedernales earthquake suggest significant postseismic deformation occurring in the early postseismic period (i.e. first few hours after the earthquake) that is not captured in daily GPS time series. To understand the characteristics of early postseismic deformation, and its relationship with the mainshock rupture area, aftershocks and longer-term postseismic deformation, we estimate the spatiotemporal distribution of early afterslip with HR-GPS time series that span ~ 2.5 minutes to 72 hours after the earthquake, and compare with afterslip models estimated with daily GPS time series spanning a similar postseismic time period and up to 30 days after the earthquake. Our inversion technique enables us to image the nucleation of afterslip in the initial hours after the earthquake, bringing us closer to the transition between the coseismic and postseismic phases. The spatial signature of early afterslip in the region updip of the mainshock rupture area is consistent with longer-term afterslip that occurs in the 30-day postseismic period, indicating that afterslip nucleated updip of and adjacent to peak coseismic slip asperities, in two localized areas, and subsequently continued to grow in amplitude with time in these specific areas. A striking difference, however, is that inversion of the 72-hour HR-GPS time series suggests early afterslip within the mainshock rupture area, but which may have been short-lived. More interestingly, we find that postseismic slip starts immediately after the earthquake at a rapid rate. Indeed, we find that early afterslip represents a significant contribution to the postseismic geodetic moment-afterslip in the first 72 hours is ~60 % greater than that estimated with daily GPS time series that span the first three post-earthquake daily GPS positions (i.e. covering the same time window). The results of our study demonstrate that imaging the spatio-temporal evolution of afterslip using subdaily GPS time series is important for evaluating postseismic slip 3 | P a g e budgets, and provides additional insights into the postseismic slip behaviour of faults.

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confidence: 99%

Imaging rapid early afterslip of the 2016 Pedernales earthquake, Ecuador

Tsang

Vergnolle

Twardzik

et al. 2019

Earth and Planetary Science Letters

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“…Luo and Ampuero (2017) performed a thorough stability analysis of an infinite frictionally heterogeneous fault. Yabe and Ide (2018;hereafter YI18) reproduced aftershocks within the mainshock rupture area (e.g., Beroza and Zoback 1993;Woessner et al 2006) by considering the partial rupture of a frictionally heterogeneous fault. Dublanchet et al (2013) and YI18 reported foreshocks before the mainshock, though no previous study has investigated the causes of variations in foreshock activity.…”

Section: Introductionmentioning

confidence: 99%

Variations in precursory slip behavior resulting from frictional heterogeneity

Yabe

Ide

2018

Prog Earth Planet Sci

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Precursory seismicity is often observed before a large earthquake. Small foreshocks occur within the mainshock rupture area, which cannot be explained by simple models that assume homogeneous friction on the entire fault. In this study, we consider a frictionally heterogeneous fault model, motivated by recent observations of geologic faults and slow earthquakes. This study investigates slip behavior on faults governed by a rate-and state-dependent friction law. We consider a finite linear fault consisting of alternating velocity-weakening zones (VWZs) and velocitystrengthening zones (VSZs). Our model generates precursory slip before the mainshock that ruptures the entire fault, though the activity level of the precursory slip depends on the frictional parameters. We investigate variations in precursory slip behavior, which we characterize quantitatively by the background slip acceleration and seismic radiation, using parameter studies of the a value of the VWZs and VSZs. The results reveal that precursory slip is very small when VWZs are strongly locked and when VSZs consume only a small amount of energy during seismic slip. Precursory slip is significant around the stability boundary of the fault. Furthermore, the type of precursory slip (seismic or aseismic) is controlled by the amplitude of the frictional heterogeneity. Active foreshocks obeying an inverse Omori law associated with background aseismic slip can be interpreted as the nucleation of the mainshock, though this is different from classical nucleation because the monotonic increase in slip velocity is significantly perturbed by the occurrence of foreshocks. Frictional heterogeneity also affects interseismic slip behavior. Modeled variations in precursory slip behavior and interseismic activity can qualitatively explain the along-dip and amongsubduction-zone variations in real seismicity patterns. Because even simple frictional heterogeneity produces complex seismicity, it is necessary to further investigate the slip behavior of frictionally heterogeneous faults, which could be utilized for modeling various real seismicity patterns.

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“…Several earthquake sequence models add frictional heterogeneity (a mixture of velocity‐weakening and ‐strengthening regions) to produces on‐fault aftershocks. For example, Yabe and Ide (2018) were successful in reproducing on‐fault aftershocks for a single planar fault by varying the sign of a − b . Kaneko and Lapusta (2008) also studied the earthquake nucleation process and aftershock sequences in the transition zone of a − b .…”

Section: Discussionmentioning

confidence: 99%

“…From the physical perspective, rerupture of part of the mainshock fault as an aftershock requires very high‐speed healing and reloading. Although some recent numerical studies show that rerupture of the main fault is possible in a subset of the parameter space (Barbot, 2019b; Cattania, 2019; Yabe & Ide, 2018), many earthquake sequence models on a flat fault with spatially variable friction often show seismic quiescence after the largest events occur (Aochi & Ide, 2009; Dublanchet et al., 2013). Therefore, it is reasonable to assume that most aftershocks are the ruptures of subsidiary faults surrounding major faults that are ruptured as mainshock, at least for intraplate earthquakes on immature faults (i.e., faults with short slip histories, which have been shown to have a more complex architecture than long‐lived, mature faults [Ben‐Zion & Sammis, 2003; Manighetti et al., 2007]), such as the Tottori event.…”

Section: Introductionmentioning

confidence: 99%

Mainshock and Aftershock Sequence Simulation in Geometrically Complex Fault Zones

Ozawa

Ando

2021

JGR Solid Earth

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The complexity of natural fault zones has been a target of numerous studies (Ben-Zion & Sammis, 2003; Faulkner et al., 2010). Although often simplified as a single flat surface in modeling, natural faults have complicated geometry. Faults are typically composed of a few discontinuous segments at a wide range of scales (Manighetti et al., 2015; Segall & Pollard, 1980). Each continuous slip surface has deviation from planarity over broad spatial scales. The fractal-like geometrical irregularity of fault surfaces is referred to as fault roughness and is documented from various observations (

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Why Do Aftershocks Occur Within the Rupture Area of a Large Earthquake?

Cited by 21 publications

References 47 publications

Imaging rapid early afterslip of the 2016 Pedernales earthquake, Ecuador

Imaging rapid early afterslip of the 2016 Pedernales earthquake, Ecuador

Variations in precursory slip behavior resulting from frictional heterogeneity

Mainshock and Aftershock Sequence Simulation in Geometrically Complex Fault Zones

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