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Resolving the Kinematics and Moment Release of Early Afterslip within the First Hours following the 2016 M_w 7.1 Kumamoto Earthquake: Implications for the Shallow Slip Deficit and Frictional Behavior of Aseismic Creep

Milliner, C. and Bürgmann, R. and Inbal, A. and Wang, T. and Liang, C. (2020) Resolving the Kinematics and Moment Release of Early Afterslip within the First Hours following the 2016 M_w 7.1 Kumamoto Earthquake: Implications for the Shallow Slip Deficit and Frictional Behavior of Aseismic Creep. Journal of Geophysical Research. Solid Earth, 125 (9). Art. No. e2019JB018928. ISSN 2169-9313. https://resolver.caltech.edu/CaltechAUTHORS:20200824-072532970

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Abstract

As stresses following rupture are dissipated continuous measurements of postseismic surface deformation provide insight into variations of the frictional strength of faults and the rheology of the lower crust and upper mantle. Due to the difficulty of capturing the earliest phase of afterslip, most analyses have focused on understanding postseismic processes over timescales of weeks to years. Here we investigate the kinematics, moment release, and frictional properties of the earliest phase of afterslip within the first hours following the 2016 M_w 7.1 Kumamoto earthquake using a network of 5‐minute sampled continuous Global Positioning System (GPS) stations. Using independent component analysis to filter the GPS data, we find that (1) early afterslip contributes only ~1% of total moment release within the first hour and 8% after 24 hr. This suggests that the lack of a coseismic slip deficit, which we estimate using standard geodetic data sets (e.g., InSAR, GPS, and pixel offsets) and which span the first 4 days of the postseismic period, is largely reflective of the dynamic rupture process and we can rule out contamination of moment release by early afterslip. (2) Early afterslip shows no evidence of a delayed nucleation or acceleration phase, where instead fault patches transition to immediate deceleration following rupture that is consistent with frictional relaxation under steady state conditions with dependence only on the sliding velocity. (3) There is a close correlation between the near‐field aftershocks and afterslip within the first hours following rupture, suggesting afterslip may still be an important possible triggering mechanism during the earliest postseismic period.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1029/2019JB018928DOIArticle
https://doi.org/10.5281/zenodo.3522444DOIData
ORCID:
AuthorORCID
Milliner, C.0000-0002-3790-595X
Bürgmann, R.0000-0002-3560-044X
Inbal, A.0000-0001-8848-7279
Wang, T.0000-0003-3729-0139
Liang, C.0000-0003-3938-426X
Additional Information:© 2020 American Geophysical Union. Issue Online: 02 September 2020; Version of Record online: 02 September 2020; Accepted manuscript online: 19 August 2020; Manuscript accepted: 14 August 2020; Manuscript revised: 31 July 2020; Manuscript received: 29 October 2019. We would like to thank Yuri Fialko and one anonymous reviewer for their helpful suggestions. We also thank David Bekaert and Adriano Gualandi for their helpful discussions. Part of this research was supported by the NASA Earth Surface and Interior focus area and performed at the Jet Propulsion Laboratory, California Institute of Technology. Funding for this project was provided under a NASA Postdoctoral Program fellowship to C. M. administered by the Universities Space and Research Association through a contract with NASA and a NASA ESI grant NNX16AL17G awarded to R. B. The authors declare that they have no competing interests. Data Availability Statement: GPS raw and filtered time series are available in the supporting information and can be downloaded from the online open access data repository site Zenodo (https://doi.org/10.5281/zenodo.3522444).
Group:Seismological Laboratory
Funders:
Funding AgencyGrant Number
NASA/JPL/CaltechUNSPECIFIED
NASA Postdoctoral ProgramUNSPECIFIED
NASANNX16AL17G
Subject Keywords:asesimic crepp; postseismic; Kumamoto; shallow slip deficit; friction; earthquake
Issue or Number:9
Record Number:CaltechAUTHORS:20200824-072532970
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20200824-072532970
Official Citation:Milliner, C., Bürgmann, R., Inbal, A., Wang, T., & Liang, C. (2020). Resolving the kinematics and moment release of early afterslip within the first hours following the 2016 Mw 7.1 Kumamoto earthquake: Implications for the shallow slip deficit and frictional behavior of aseismic creep. Journal of Geophysical Research: Solid Earth, 125, e2019JB018928. https://doi.org/10.1029/2019JB018928
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:105065
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:24 Aug 2020 16:21
Last Modified:10 Sep 2020 20:53

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