Seismic Rhythms: Earthquake Response to Tectonic, Hydrological, and Tidal Forcing in California

Krittanon Sirorattanakul; Jean-Philippe Avouac

doi:10.1126/sciadv.adz5711

Seismic Rhythms: Earthquake Response to Tectonic, Hydrological, and Tidal Forcing in California

Krittanon Sirorattanakul
, Jean-Philippe Avouac

Seismological Laboratory

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Abstract

Seismicity is primarily driven by tectonics, but stress variations of natural or human-made origin can induce detectable modulations, offering insights into earthquake physics. Here, we identify regions in California exhibiting significant seasonal modulations of seismicity rate linked to hydrological surface loading but no significant semidiurnal tidal modulation. The peak seismicity rate lags behind the peak stressing rate by half a month. Assuming instantaneous nucleation substantially overpredicts the response, whereas time-dependent nucleation governed by rate-and-state friction accurately captures both the amplitude and the time delay with friction-stress parameter aσ ~ 1 to 10 kilopascals (kPa) and characteristic relaxation time t a ~ 0.05 to 1 year. The seismicity response to tidal and seasonal stress perturbations allows us to probe fault mechanical properties, providing a way to improve seismic hazard assessment.

Original language	English
Article number	eadz5711
Pages (from-to)	1-42
Number of pages	42
Journal	Science Advances
Volume	12
Issue number	13
DOIs	https://doi.org/10.1126/sciadv.adz5711
Publication status	Published (in print/issue) - 25 Mar 2026

Bibliographical note

Publisher Copyright:
copyright © 2026 the Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. no claim to original U.S. Government Works. distributed under a creative commons Attribution noncommercial license 4.0 (cc BY-nc).

Data Availability Statement

All data and code needed to evaluate and reproduce the results in the paper are present in the paper, the Supplementary Materials, or is available online at the CaltechDATA repository at https://doi.org/10.22002/wgvt5-6qs27. This study did not generate new materials.

Funding

This study is supported by the US National Science Foundation (NSF) grant no. EAR-2142152 and the NSF/Industry-University Collaborative Research Center “Geomechanics and Mitigation of Geohazards (NSF award no. 1822214) awarded to J.-P.A.

UN SDGs

This output contributes to the following UN Sustainable Development Goals (SDGs)

SDG 11 Sustainable Cities and Communities
SDG 13 Climate Action

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10.1126/sciadv.adz5711Licence: CC BY-NC

Seismic Rythms-Final VersionFinal published version, 4.28 MBLicence: CC BY-NC

Cite this

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title = "Seismic Rhythms: Earthquake Response to Tectonic, Hydrological, and Tidal Forcing in California",

abstract = "Seismicity is primarily driven by tectonics, but stress variations of natural or human-made origin can induce detectable modulations, offering insights into earthquake physics. Here, we identify regions in California exhibiting significant seasonal modulations of seismicity rate linked to hydrological surface loading but no significant semidiurnal tidal modulation. The peak seismicity rate lags behind the peak stressing rate by half a month. Assuming instantaneous nucleation substantially overpredicts the response, whereas time-dependent nucleation governed by rate-and-state friction accurately captures both the amplitude and the time delay with friction-stress parameter aσ \textasciitilde{} 1 to 10 kilopascals (kPa) and characteristic relaxation time t a \textasciitilde{} 0.05 to 1 year. The seismicity response to tidal and seasonal stress perturbations allows us to probe fault mechanical properties, providing a way to improve seismic hazard assessment. ",

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Seismic Rhythms: Earthquake Response to Tectonic, Hydrological, and Tidal Forcing in California

Abstract

Bibliographical note

Data Availability Statement

Funding

UN SDGs

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