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On the relationship between strain rate and seismicity in the India–Asia collision zone: implications for probabilistic seismic hazard

Stevens, V. L. and Avouac, J.-P. (2021) On the relationship between strain rate and seismicity in the India–Asia collision zone: implications for probabilistic seismic hazard. Geophysical Journal International, 226 (1). pp. 220-245. ISSN 0956-540X. doi:10.1093/gji/ggab098.

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The increasing density of geodetic measurements makes it possible to map surface strain rate in many zones of active tectonics with unprecedented spatial resolution. Here we show that the strain tensor rate calculated from GPS in the India–Asia collision zone represents well the strain released in earthquakes. This means that geodetic data in the India–Asia collision zone region can be extrapolated back in time to estimate strain buildup on active faults, or the kinematics of continental deformation. We infer that the geodetic strain rates can be assumed stationary through time on the timescale needed to build up the elastic strain released by larger earthquakes, and that they can be used to estimate the probability of triggering earthquakes. We show that the background seismicity rate correlates with the geodetic strain rate. A good fit is obtained assuming a linear relationship (⁠˙N=λ ⋅˙ϵ⁠, where ˙N is the density of the rate of M_w ≥ 4 earthquakes, ˙ϵ is strain rate and λ = 2.5 ± 0.1 × 10⁻³ m⁻²), as would be expected from a standard Coulomb failure model. However, the fit is significantly better for a non-linear relationship (⁠˙N=γ₁⋅˙ϵ^(γ₂) with γ₁ = 2.5 ± 0.6 m⁻² and γ₂ = 1.42 ± 0.15). The b-value of the Gutenberg–Richter law, which characterize the magnitude–frequency distribution, is found to be insensitive to the strain rate. In the case of a linear correlation between seismicity and strain rate, the maximum magnitude earthquake, derived from the moment conservation principle, is expected to be independent of the strain rate. By contrast, the non-linear case implies that the maximum magnitude earthquake would be larger in zones of low strain rate. We show that within areas of constant strain rate, earthquakes above M_w 4 follow a Poisson distribution in time and and are uniformly distributed in space. These findings provide a framework to estimate the probability of occurrence and magnitude of earthquakes as a function of the geodetic strain rate. We describe how the seismicity models derived from this approach can be used as an input for probabilistic seismic hazard analysis. This method is easy to automatically update, and can be applied in a consistent manner to any continental zone of active tectonics with sufficient geodetic coverage.

Item Type:Article
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URLURL TypeDescription
Stevens, V. L.0000-0003-3174-9949
Avouac, J.-P.0000-0002-3060-8442
Additional Information:© The Author(s) 2021. Published by Oxford University Press on behalf of The Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model ( Accepted 2021 March 9. Received 2021 March 1; in original form 2020 November 8. Published: 11 March 2021. We would like to thank Peter Bird and Chris Rollins for constructive and detailed reviews of this manuscript. VLS was supported by the Claude Leon Foundation. This work was partially supported by NSF award EAR-1821853. Data Availability: No new data were generated or analysed in support of this research. All data used in this study is already publicly available.
Group:Center for Geomechanics and Mitigation of Geohazards (GMG), Division of Geological and Planetary Sciences, Seismological Laboratory
Funding AgencyGrant Number
Claude Leon FoundationUNSPECIFIED
Subject Keywords:Earthquake hazards, Fractures, faults, and high strain deformation zones, Seismicity and tectonics, Asia
Issue or Number:1
Record Number:CaltechAUTHORS:20210910-231037057
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Official Citation:V L Stevens, J-P Avouac, On the relationship between strain rate and seismicity in the India–Asia collision zone: implications for probabilistic seismic hazard, Geophysical Journal International, Volume 226, Issue 1, July 2021, Pages 220–245,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:110820
Deposited By: Tony Diaz
Deposited On:13 Sep 2021 17:30
Last Modified:15 Nov 2022 21:48

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