Publication Date:
2017-05-21
Description:
The 2016 M7.8 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 distance Dc", 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 estimated Dc" 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 inferred Dc" is the largest value ever estimated from near-fault strong motion data, yet it appears to follow the scaling of Dc" with final slip for several large strike-slip earthquakes. The energy budget of the M7.8 Kaikōura earthquake inferred from the scaling of Dc" 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). ©2017. American Geophysical Union. All Rights Reserved.
Print ISSN:
0094-8276
Electronic ISSN:
1944-8007
Topics:
Geosciences
,
Physics
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