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Slip‐weakening distance and energy budget inferred from near‐fault ground deformation during the 2016 M w 7.8 Kaikōura earthquake
Author(s) -
Kaneko Yoshihiro,
Fukuyama Eiichi,
Hamling Ian James
Publication year - 2017
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 - 10.1002/2017gl073681
Subject(s) - seismology , geology , slip (aerodynamics) , geodetic datum , fault trace , geodesy , scaling , strong ground motion , fault (geology) , elastic rebound theory , seismic gap , ground motion , geometry , physics , mathematics , thermodynamics
The 2016 M 7.8 Kaikōura (New Zealand) earthquake struck the east coast of the northern South Island, resulting in strong ground shaking and large surface fault slip. Since the earthquake was well recorded by a local strong‐motion seismic network, near‐fault data may provide direct measurements of dynamic parameters associated with the fault‐weakening process. Here we estimate a proxy for slip‐weakening distanceD c′′ , defined as double the fault‐parallel displacement at the time of peak ground velocity, from accelerograms recorded at a near‐fault station. Three‐component ground displacements were recovered from the double numerical integration of accelerograms, and the corresponding final displacements are validated against coseismic displacement from geodetic data. The estimatedD c′′is 4.9 m at seismic station KEKS located ∼2.7 km from a segment of the Kekerengu fault where large surface fault slip (∼12 m) has been observed. The inferredD c′′is the largest value ever estimated from near‐fault strong motion data, yet it appears to follow the scaling ofD c′′with final slip for several large strike‐slip earthquakes. The energy budget of the M 7.8 Kaikōura earthquake inferred from the scaling ofD c′′with final slip indicates that a large amount of energy was dissipated by on‐ and off‐fault inelastic deformation during the propagation of the earthquake rupture, resulting in a slower average rupture speed ( ≲ 2.0 km/s).