Illuminating a Contorted Slab with a Complex Intraslab Rupture Evolution during the 2021 Mw 7.3 East Cape, New Zealand Earthquake

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Ryo Okuwaki , Stephen Paul Hicks , Timothy J Craig, Wenyuan Fan, Saskia Goes , Tim J Wright, Yagi Yuji


The state-of-stress within subducting oceanic plates controls rupture processes of deep intraslab earthquakes. However, little is known about how the large-scale plate geometry and the stress regime relate to the physical nature of the deep-intraslab earthquakes. Here we find, by using globally and locally observed seismic records, that the moment magnitude 7.3 2021 East Cape, New Zealand earthquake was driven by a combination of shallow trench-normal extension and unexpectedly, deep trench-parallel compression. We find multiple rupture episodes comprising a mixture of reverse, strike-slip, and normal faulting. Reverse faulting due to the trench-parallel compression is unexpected given the apparent subduction direction, so we require a differential-buoyancy driven stress rotation which contorts the slab near the edge of the Hikurangi plateau. Our finding highlights that buoyant features in subducting plates may cause diverse rupture behavior of intraslab earthquakes due to the resulting heterogeneous stress state within slabs.



Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics


earthquake rupture, slab geometry, intraslab earthquakes, source imaging, finite-fault inversion, Hikurangi


Published: 2021-07-18 06:59

Last Updated: 2021-11-25 02:13

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