Afterslip Moment Scaling and Variability From a Global Compilation of Estimates

Churchill, R. M.; Werner, Maximilian J.; Biggs, Juliet; Fagereng, Åke

doi:10.1029/2021jb023897

Cited by 18 publications

(31 citation statements)

References 153 publications

(273 reference statements)

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“…We agree with Churchill et al. (2022) that model uncertainties pose a challenge for afterslip estimation. We also cannot constrain the first 2 days after the mainshock (15–17 May) geodetically due to a lack of SAR data.…”

Section: Resultssupporting

confidence: 93%

“…For example, we can produce models that match the low seismic moment from aftershocks but have unreasonably high misfits or that far exceed our preferred moment estimates but are unreasonably rough. We agree with Churchill et al (2022) that model uncertainties pose a challenge for afterslip estimation. We also cannot constrain the first 2 days after the mainshock (15-17 May) geodetically due to a lack of SAR data.…”

Section: Resultssupporting

confidence: 87%

“…The relatively low ratio for the blind, immature fault that ruptured in the MCR earthquake tentatively supports the weak correlation between fault maturity and the ratio of afterslip to coseismic moment postulated in Churchill et al. (2022). Our results, though, indicate that moment release on the western segment, which could be a direct extension of the mapped Candelaria fault further west (Wesnousky, 2005), was dominated by coseismic slip.…”

Section: Resultssupporting

confidence: 72%

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Afterslip From the 2020 M 6.5 Monte Cristo Range, Nevada Earthquake

Chorsi

Braunmiller

Deng

et al. 2022

Geophysical Research Letters

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Measurements of surface deformation after an earthquake can be used to probe the frictional properties of the earthquake fault and the rheological properties of the crust and upper mantle. Large magnitude earthquakes (approximately M > 7) can stress deeper parts of the Earth's crust and upper mantle; their postseismic motions likely reflect a range of processes and properties, including afterslip, viscous relaxation of the lower crust and/or upper mantle, and poroelastic effects. In contrast, stress changes associated with smaller magnitude events may only affect the upper and middle crust and may exhibit a more limited range of postseismic phenomena. Whether a deformation process is active or not likely depends in part on stress change magnitude. Studying postseismic responses for a range of earthquake magnitudes is therefore important.Until recently, studies of the postseismic response of smaller magnitude earthquakes were challenged by low signal to noise ratios. However, improvement in geodetic techniques, such as GPS and InSAR, now permits such studies. Here, we present geodetic and seismic data covering the first 7 months after the 15 May 2020, M w 6.5 Monte Cristo Range (MCR), Nevada, earthquake. Combined seismic and geodetic data suggest that aseismic afterslip on the main fault plane dominates the postseismic response. We focus on three questions:1. What is the ratio of seismic to aseismic afterslip? 2. How is postseismic slip distribution related to coseismic slip and surface rupture? 3. Does afterslip reduce the shallow slip deficit (difference between surface slip and slip at depth)?

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Section: Resultssupporting

confidence: 93%

Section: Resultssupporting

confidence: 87%

Section: Resultssupporting

confidence: 72%

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Afterslip From the 2020 M 6.5 Monte Cristo Range, Nevada Earthquake

Chorsi

Braunmiller

Deng

et al. 2022

Geophysical Research Letters

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“…Given that the amplitude of postseismic deformation scales with the coseismic moment [Churchill et al, 2022], our new estimate of the coseismic moment of the 2011 Mochiyama earthquake will have important implications for the predicted postseismic deformation. The likely explanation for the difference between the seismic and geodetic moment estimates is that the interferograms used by Fukushima et al [2018] to invert for the pattern of slip in the 19th March 2011 Mochiyama earthquake (which span the dates 2011/02/02-2011/03/20 for the ascending track and 2010/11/20-2011/04/07 for the descending track) contain some surface deformation that was not caused by coseismic slip.…”

Section: Long-period Body-waveform Modellingmentioning

confidence: 99%

Time-Dependent Decrease in Fault Strength in the 2011--2016 Ibaraki-Fukushima Earthquake Sequence

Wimpenny¹,

Forrest²,

Copley³

2022

Preprint

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Two near-identical Mw 5.8 earthquakes in 2011 and 2016 ruptured the Mochiyama Fault in North Kanto, Japan. The unusually short repeat time between the Mochiyama earthquakes provides a rare opportunity estimate the evolution of stress on a fault through an earthquake cycle, as the stress drop in the first earthquake provides a reference from which we can infer variations through time in the stresses required to cause earthquake rupture. By combining observations of deformation from GPS, InSAR and seismology with numerical models of stress transfer due to coseismic deformation and postseismic relaxation, we demonstrate that the rupture area on the Mochiyama Fault could only have been re-loaded by 35--50\% of the 2011 earthquake stress drop over the period between the 2011 and 2016 earthquakes. We infer that the Mochiyama Fault became weaker in the intervening 6 years, with a 2--10 MPa drop in the shear stresses needed to break the fault in earthquakes. The mechanism(s) that led to this weakening are unclear, but were associated with extensive aftershock seismicity that released a cumulative moment similar to the 2011 mainshock. Temporal changes in fault strength may therefore play a role in modulating the timing of moderate-magnitude earthquakes.

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“…Data used are accessible through: Churchill et al. (2022), https://doi.org/10.5281/zenodo.6414330, and USGS (2017). Also accessible are our aftershock selection codes: https://doi.org/10.5281/zenodo.7188981 (including our NND catalog), the Omori fitter: https://github.com/tgoebel/aftershocks, b ‐value/ M c analysis codes: https://github.com/sachalapins/bvalues, and the Lillliefors b ‐value test: https://doi.org/10.5281/zenodo.4162497.…”

Section: Data Availability Statementmentioning

confidence: 99%

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

Churchill

Werner

Biggs

et al. 2022

Geophysical Research Letters

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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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Afterslip Moment Scaling and Variability From a Global Compilation of Estimates

Abstract: Following an earthquake, various postseismic mechanisms act to relax and redistribute stress concentrations in the crust and upper mantle (Freed, 2005). In addition to seismic aftershocks, postseismic mechanisms include aseismic afterslip (

Cited by 18 publications

References 153 publications

Afterslip From the 2020 M 6.5 Monte Cristo Range, Nevada Earthquake

Afterslip From the 2020 M 6.5 Monte Cristo Range, Nevada Earthquake

Time-Dependent Decrease in Fault Strength in the 2011--2016 Ibaraki-Fukushima Earthquake Sequence

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

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