Abstract
Damaging aftershock sequences often exhibit considerable spatio-temporal complexity. The stress changes associated with coseismic slip and aseismic afterslip are commonly proposed to drive aftershock sequences, but few systematic studies exist and do not always support strong, universal driving relationships. To investigate the roles that these two sources of stress changes may play in driving aftershocks, we assess the spatio-temporal relationships between coseismic slip, afterslip, and on-fault (within 5 km) aftershock density following seven Mw6.0–7.6 continental-settings earthquakes, using available high-quality slip models and regional seismic data. From previous empirical work and frictional considerations, near the mainshock we expect coseismic slip and afterslip to be anti-correlated, and aftershocks to occur where coseismic slip is low/zero, near high slip gradients, and/or to migrate with afterslip. However, we find that spatial relationships between afterslip and coseismic slip, and between afterslip and aftershock density differ between earthquakes. Aftershock density correlates with coseismic slip following five of the earthquakes, and with total cumulative slip (coseismic slip + afterslip) following six: indicating that on-fault aftershock distributions may be approximated by total slip (at current resolutions). Additionally, we find that the gradients of coseismic slip and afterslip (proxies for new stress concentrations) do not clearly correlate with aftershock distributions and that the choice of spatial domain over which relationships are tested can affect results significantly. A possible explanation of these results is that fault zones contain considerable fine-scale structural and frictional heterogeneity. Nonetheless, the empirical evidence for frequently assumed relationships between coseismic slip, afterslip and on-fault aftershocks is mixed.
| Original language | English |
|---|---|
| Article number | e2023JB027168 |
| Journal | Journal of Geophysical Research: Solid Earth |
| Volume | 129 |
| Issue number | 1 |
| DOIs | |
| Publication status | Published - 23 Jan 2024 |
Bibliographical note
Funding Information:R. M. Churchill and M. J. Werner were supported by the European Union H2020 program (Grant 821115, Real‐time earthquake rIsk reduction for a reSilient Europe [RISE]). R. M. Churchill acknowledges the support of a NERC GW4+ Doctoral Training Partnership studentship [NE/L002434/1]. J. Biggs and M. J. Werner were also funded by the NERC Centre for the Observation and Modelling of Earthquakes, Volcanoes and Tectonics (COMET, http://comet.nerc.ac.uk ), a partnership between UK Universities and the British Geological Survey. J. Biggs is also funded by a Leverhulme Prize (PLP‐2018‐362). A. Fagereng received funding from the European Union H2020 programme, ERC Starting Grant MICA [No 715836]. We thank the following individuals who provided, or helped find, coseismic and afterslip models: Roland Bürgmann, Daniele Cheloni, Nicola D’Agostino, Semih Ergintav, Wangpeng Feng, Elizabeth Hearn, Junle Jiang, Fred Pollitz, Chris Rollins, Elisa Trasatti, Kang Wang, Sam Wimpenny, and Han Yue. We thank Robert Myhill and Jessica Hawthorne for discussion that improved this work. We thank Kelian Dascher‐Cousineau, an anonymous second reviewer, Rachel Abercrombie, and the Associate Editor for reviews which also improved this manuscript.
Funding Information:
R. M. Churchill and M. J. Werner were supported by the European Union H2020 program (Grant 821115, Real-time earthquake rIsk reduction for a reSilient Europe [RISE]). R. M. Churchill acknowledges the support of a NERC GW4+ Doctoral Training Partnership studentship [NE/L002434/1]. J. Biggs and M. J. Werner were also funded by the NERC Centre for the Observation and Modelling of Earthquakes, Volcanoes and Tectonics (COMET, http://comet.nerc.ac.uk), a partnership between UK Universities and the British Geological Survey. J. Biggs is also funded by a Leverhulme Prize (PLP-2018-362). A. Fagereng received funding from the European Union H2020 programme, ERC Starting Grant MICA [No 715836]. We thank the following individuals who provided, or helped find, coseismic and afterslip models: Roland Bürgmann, Daniele Cheloni, Nicola D’Agostino, Semih Ergintav, Wangpeng Feng, Elizabeth Hearn, Junle Jiang, Fred Pollitz, Chris Rollins, Elisa Trasatti, Kang Wang, Sam Wimpenny, and Han Yue. We thank Robert Myhill and Jessica Hawthorne for discussion that improved this work. We thank Kelian Dascher-Cousineau, an anonymous second reviewer, Rachel Abercrombie, and the Associate Editor for reviews which also improved this manuscript.
Publisher Copyright:
© 2024. The Authors.