Excitation of San Andreas tremors by thermal instabilities below the seismogenic zone

Wang, Lifeng; Barbot, Sylvain

doi:10.1126/sciadv.abb2057

Cited by 25 publications

(20 citation statements)

References 47 publications

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“…However, more imminent seismic hazard in Kathmandu may originate from seismic ruptures that break different sections of the Himalayan megathrust, initiating outside the Kathmandu Klippe 7 . Different scenarios of future seismicity are also possible due to the many remaining unknown mechanical properties of the plate boundary, including deformation of the upper plate by faulting and folding 8,48 , more complex frictional behaviour of the megathrust 49 , and interactions with other segments of the Himalayan megathrust 50 .…”

Section: Discussionmentioning

confidence: 99%

The stop-start control of seismicity by fault bends along the Main Himalayan Thrust

Sathiakumar

Barbot

2021

Commun Earth Environ

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The Himalayan megathrust accommodates most of the relative convergence between the Indian and Eurasian plates, producing cycles of blind and surface-breaking ruptures. Elucidating the mechanics of down-dip segmentation of the seismogenic zone is key to better determine seismic hazards in the region. However, the geometry of the Himalayan megathrust and its impact on seismicity remains controversial. Here, we develop seismic cycle simulations tuned to the seismo-geodetic data of the 2015 Mw 7.8 Gorkha, Nepal earthquake to better constrain the megathrust geometry and its role on the demarcation of partial ruptures. We show that a ramp in the middle of the seismogenic zone is required to explain the termination of the coseismic rupture and the source mechanism of up-dip aftershocks consistently. Alternative models with a wide décollement can only explain the mainshock. Fault structural complexities likely play an important role in modulating the seismic cycle, in particular, the distribution of rupture sizes. Fault bends are capable of both obstructing rupture propagation as well as behave as a source of seismicity and rupture initiation.

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Section: Discussionmentioning

confidence: 99%

The stop-start control of seismicity by fault bends along the Main Himalayan Thrust

Sathiakumar

Barbot

2021

Commun Earth Environ

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“…We conclude that variations in potency density among slow‐slip events preclude a simple characterization in terms of a linear or cubic root scaling between moment and duration. Several micro‐physical mechanisms of deformation may be responsible for the slow‐slip phenomenon, including stable weakening (Liu & Rice, 2005, 2007; Veedu & Barbot, 2016), dilatant hardening (Segall et al, 2010), semi‐brittle deformation (Goswami & Barbot, 2018), fluid pulses (Cruz‐Atienza et al, 2018), and thermal instabilities (Wang & Barbot, 2020). In addition, some slow‐slip events do not occur spontaneously but are triggered by distant seismic events (Zigone et al, 2012).…”

Section: Discussionmentioning

confidence: 99%

Static Source Properties of Slow and Fast Earthquakes

2020

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The source characteristics of slow and fast earthquakes provide a window into the mechanical properties of faults. In particular, the average stress drop controls the evolution of friction, fault slip, and event magnitude. However, this important source property is typically inferred from the analysis of seismic waves and is subject to many epistemic uncertainties. Here, we investigate the source properties of 53 earthquakes and 17 slow-slip events on thrust and strike-slip faults in various tectonic settings using slip distributions constrained by geodesy in combination with other data. We determine the width, potency, and potency density of slow and fast earthquake sources based on static slip distributions. The potency density, defined conceptually as the ratio of average slip to rupture radius, is a measure of anelastic deformation with limited bias from rigidity differences across depths and tectonic settings. Strike-slip earthquakes have the highest potency density, varying from 20 to 500 microstrain. The potency density is on average lower on continental thrust faults and megathrusts, from 10 to 200 microstrain, with an algebraic decrease with centroid depth, indicative of systematic changes in dominant rupture processes with depth. Slow slip events represent an end-member style of rupture with low potency density and large rupture width. Significant variability in potency density of slow-slip events affects their moment-duration scaling. The variations of source properties across tectonic settings, depth, and rupture styles can be used to better constrain numerical simulations of seismicity and to assess the source characteristics of future earthquakes and slow slip events. Plain Language Summary Natural earthquakes reduce the stress that accumulates on faults due to plate tectonics. To better understand the variability of seismic hazards around active faults, we survey the properties of slow and fast earthquakes around the world. The potential of faults to concentrate large slip in the rupture area differs depending on the geological setting, the depth of the source, and the type of rupture. Earthquakes in a continental setting condense more slip in a given rupture area, particularly in transform faults like the San Andreas fault. Subduction zone earthquakes, although some of the largest events on Earth, generally distribute less slip over a wider area, but this varies as a function of depth. Slow earthquakes represent an extreme case of little slip distributed over a large area. The propensity of rupture characteristics to vary with fault type and depth may help forecast the hazards posed by future seismicity.

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“…

Slow earthquakes are mainly observed in regions surrounding seismogenic zones, which are the areas that rupture in large regular earthquakes, along the plate boundaries of subduction zones (e.g., Obara & Kato, 2016) or strike-slip faults (e.g., Nadeau & Dolenc, 2005;Wang & Barbot, 2020). Various types of slow earthquakes, such as low frequency tremors (tectonic tremors; e.g., Obara, 2002), low frequency earthquakes (LFEs; e.g., Shelly et al, 2006), very low frequency earthquakes (VLFEs; e.g., Obara & Ito, 2005), and slow slip events (SSEs; e.g., Dragert et al, 2001) have been observed in many subduction zones.

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confidence: 99%

Shallow Slow Earthquake Episodes Near the Trench Axis off Costa Rica

et al. 2021

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Slow earthquakes are mainly distributed in regions surrounding seismogenic zones along the plate boundaries of subduction zones. In the Central American subduction zone, large regular interplate earthquakes with magnitudes of 7–8 occur repeatedly around the Nicoya Peninsula, in Costa Rica, and a tsunami earthquake occurred off Nicaragua, just north of Costa Rica, in 1992. To clarify the spatial distribution of various slip behaviors at the plate boundary, we detected and located very low frequency earthquakes (VLFEs) around the Nicoya Peninsula using a grid‐search matched‐filter technique with synthetic templates based on a regional three‐dimensional model. VLFEs were active in September 2004 and August 2005, mainly near the trench axis, updip of the seismogenic zone. The distribution of VLFEs overlapped with large slip areas of slow slip events. Low frequency tremor signals were also found in high‐frequency seismogram envelopes within the same time windows as detected VLFEs; thus, we also investigated the energy rates of tremors accompanied by VLFEs. The range of scaled energy, which is the ratio of the seismic energy rate of a tremor to the seismic moment rate of accompanying VLFE and related to the rupture process of seismic phenomena, was 10−9–10−8. The along‐dip separation of shallow slow and large earthquakes and the range of the scaled energy off Costa Rica are similar to those in shallow slow earthquakes in Nankai, which shares a similar thermal structure along the shallow plate boundary.

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Excitation of San Andreas tremors by thermal instabilities below the seismogenic zone

Cited by 25 publications

References 47 publications

The stop-start control of seismicity by fault bends along the Main Himalayan Thrust

The stop-start control of seismicity by fault bends along the Main Himalayan Thrust

Static Source Properties of Slow and Fast Earthquakes

Shallow Slow Earthquake Episodes Near the Trench Axis off Costa Rica

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