Relative Afterslip Moment Does Not Correlate With Aftershock Productivity: Implications for the Relationship Between Afterslip and Aftershocks

Robert Churchill; Max Werner; Juliet J Biggs; Ake Fagereng

doi:10.1029/2022GL101165

Relative Afterslip Moment Does Not Correlate With Aftershock Productivity: Implications for the Relationship Between Afterslip and Aftershocks

Robert Churchill^*, Max Werner, Juliet J Biggs, Ake Fagereng

^*Corresponding author for this work

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Abstract

Aseismic afterslip has been proposed to drive aftershock sequences. Both afterslip moment and aftershock number broadly increase with mainshock size, but can vary beyond this scaling. We examine whether relative afterslip moment (afterslip moment/mainshock moment) correlates with several key aftershock sequence characteristics, including aftershock number and cumulative moment (both absolute and relative to mainshock size), seismicity rate change, b-value, and Omori decay exponent. We select Mw ≥ 4.5 aftershocks for 41 tectonically varied mainshocks with available afterslip models. Against expectation, relative afterslip moment does not correlate with tested aftershock characteristics or background seismicity rate. Furthermore, adding afterslip moment to mainshock moment does not improve predictions of aftershock number. Our findings place useful empirical constraints on the link between afterslip and potentially damaging Mw ≥ 4.5 aftershocks and raise questions regarding the role afterslip plays in aftershock generation.

Original language	English
Article number	e2022GL101165
Journal	Geophysical Research Letters
Volume	49
Issue number	24
Early online date	16 Dec 2022
DOIs	https://doi.org/10.1029/2022GL101165
Publication status	Published - 28 Dec 2022

Bibliographical note

Funding Information:
R. M. Churchill is supported by a Natural Environment Research Council (NERC) GW4+ DTP studentship (NE/L002434/1). M. J. Werner received funding from RISE (821115). J. Biggs and M. J. Werner are 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 MICA (715836). We thank S. Lapins for his b-value/Mc codes and Kelian Dascher-Cousineau and two other reviewers for comments that improved this study.

Funding Information:
R. M. Churchill is supported by a Natural Environment Research Council (NERC) GW4+ DTP studentship (NE/L002434/1). M. J. Werner received funding from RISE (821115). J. Biggs and M. J. Werner are 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 MICA (715836). We thank S. Lapins for his ‐value/ codes and Kelian Dascher‐Cousineau and two other reviewers for comments that improved this study. b M c

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© 2022. The Authors.

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title = "Relative Afterslip Moment Does Not Correlate With Aftershock Productivity: Implications for the Relationship Between Afterslip and Aftershocks",

abstract = "Aseismic afterslip has been proposed to drive aftershock sequences. Both afterslip moment and aftershock number broadly increase with mainshock size, but can vary beyond this scaling. We examine whether relative afterslip moment (afterslip moment/mainshock moment) correlates with several key aftershock sequence characteristics, including aftershock number and cumulative moment (both absolute and relative to mainshock size), seismicity rate change, b-value, and Omori decay exponent. We select Mw ≥ 4.5 aftershocks for 41 tectonically varied mainshocks with available afterslip models. Against expectation, relative afterslip moment does not correlate with tested aftershock characteristics or background seismicity rate. Furthermore, adding afterslip moment to mainshock moment does not improve predictions of aftershock number. Our findings place useful empirical constraints on the link between afterslip and potentially damaging Mw ≥ 4.5 aftershocks and raise questions regarding the role afterslip plays in aftershock generation.",

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note = "Funding Information: R. M. Churchill is supported by a Natural Environment Research Council (NERC) GW4+ DTP studentship (NE/L002434/1). M. J. Werner received funding from RISE (821115). J. Biggs and M. J. Werner are 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 MICA (715836). We thank S. Lapins for his b-value/Mc codes and Kelian Dascher-Cousineau and two other reviewers for comments that improved this study. Funding Information: R. M. Churchill is supported by a Natural Environment Research Council (NERC) GW4+ DTP studentship (NE/L002434/1). M. J. Werner received funding from RISE (821115). J. Biggs and M. J. Werner are 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 MICA (715836). We thank S. Lapins for his ‐value/ codes and Kelian Dascher‐Cousineau and two other reviewers for comments that improved this study. b M c Publisher Copyright: {\textcopyright} 2022. The Authors.",

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AU - Werner, Max

AU - Biggs, Juliet J

AU - Fagereng, Ake

N1 - Funding Information: R. M. Churchill is supported by a Natural Environment Research Council (NERC) GW4+ DTP studentship (NE/L002434/1). M. J. Werner received funding from RISE (821115). J. Biggs and M. J. Werner are 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 MICA (715836). We thank S. Lapins for his b-value/Mc codes and Kelian Dascher-Cousineau and two other reviewers for comments that improved this study. Funding Information: R. M. Churchill is supported by a Natural Environment Research Council (NERC) GW4+ DTP studentship (NE/L002434/1). M. J. Werner received funding from RISE (821115). J. Biggs and M. J. Werner are 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 MICA (715836). We thank S. Lapins for his ‐value/ codes and Kelian Dascher‐Cousineau and two other reviewers for comments that improved this study. b M c Publisher Copyright: © 2022. The Authors.

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N2 - Aseismic afterslip has been proposed to drive aftershock sequences. Both afterslip moment and aftershock number broadly increase with mainshock size, but can vary beyond this scaling. We examine whether relative afterslip moment (afterslip moment/mainshock moment) correlates with several key aftershock sequence characteristics, including aftershock number and cumulative moment (both absolute and relative to mainshock size), seismicity rate change, b-value, and Omori decay exponent. We select Mw ≥ 4.5 aftershocks for 41 tectonically varied mainshocks with available afterslip models. Against expectation, relative afterslip moment does not correlate with tested aftershock characteristics or background seismicity rate. Furthermore, adding afterslip moment to mainshock moment does not improve predictions of aftershock number. Our findings place useful empirical constraints on the link between afterslip and potentially damaging Mw ≥ 4.5 aftershocks and raise questions regarding the role afterslip plays in aftershock generation.

AB - Aseismic afterslip has been proposed to drive aftershock sequences. Both afterslip moment and aftershock number broadly increase with mainshock size, but can vary beyond this scaling. We examine whether relative afterslip moment (afterslip moment/mainshock moment) correlates with several key aftershock sequence characteristics, including aftershock number and cumulative moment (both absolute and relative to mainshock size), seismicity rate change, b-value, and Omori decay exponent. We select Mw ≥ 4.5 aftershocks for 41 tectonically varied mainshocks with available afterslip models. Against expectation, relative afterslip moment does not correlate with tested aftershock characteristics or background seismicity rate. Furthermore, adding afterslip moment to mainshock moment does not improve predictions of aftershock number. Our findings place useful empirical constraints on the link between afterslip and potentially damaging Mw ≥ 4.5 aftershocks and raise questions regarding the role afterslip plays in aftershock generation.

U2 - 10.1029/2022GL101165

DO - 10.1029/2022GL101165

M3 - Article (Academic Journal)

SN - 0094-8276

VL - 49

JO - Geophysical Research Letters

JF - Geophysical Research Letters

IS - 24

M1 - e2022GL101165

ER -

Relative Afterslip Moment Does Not Correlate With Aftershock Productivity: Implications for the Relationship Between Afterslip and Aftershocks

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