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Intermediate‐Magnitude Postseismic Slip Follows Intermediate‐Magnitude ( M 4 to 5) Earthquakes in California
Author(s) -
Alwahedi M. A.,
Hawthorne J. C.
Publication year - 2019
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2018gl081001
Subject(s) - moment magnitude scale , magnitude (astronomy) , seismology , geology , slip (aerodynamics) , earthquake magnitude , borehole , san andreas fault , geodesy , seismic moment , fault (geology) , geometry , geotechnical engineering , physics , mathematics , astronomy , scaling , thermodynamics
Abstract The magnitude of postseismic slip is useful for constraining physical models of fault slip. Here we examine the postseismic slip following intermediate‐magnitude ( M 4 to 5) earthquakes by systematically analyzing data from borehole strainmeters in central and northern California. We assess the noise in the data and identify 11 earthquakes that generated interpretable strain records. We estimate the earthquakes' postseismic to coseismic moment ratios by comparing the coseismic strain changes with strain changes induced by afterslip in the following 1.5 days. The median estimated postseismic moment is 0.45 times the coseismic moment, with a 90% confidence interval between 0.25 and 0.60. This postseismic moment is slightly larger than typically observed following large ( M > 6) earthquakes but smaller than observed following small ( M 2 to 4) earthquakes. The intermediate‐magnitude postseismic slip suggests a size dependence in the dynamics of earthquakes or in the properties of fault areas that surround earthquakes.