Deep tremor in New Zealand triggered by the 2010 Mw8.8 Chile earthquake

Abstract

Deep non‐volcanic tremor (NVT) is usually associated with episodic slow‐slip events. New Zealand is one notable exception where numerous slow slip events have been identified, yet NVT has remained undetected. Here we present the first known case of triggered NVT at New Zealand's Hikurangi subduction margin. Following the Mw8.8 Chilean earthquake of February 27, 2010, we identify coherent high‐frequency tremor signals that are in phase with, and modulated by, the passing Rayleigh waves. This is consistent with the surface wave triggering potential for strike‐normal incidence on a low‐angle thrust fault. After constraining the tremor depth on the plate interface, we locate the tremor source within 20 km of the source area of episodic slow slip. The tremor location is also near the edge of a region with high seismic attenuation that marks the boundary between dehydrated subducted slab and inferred hydrated, underplated sediment. We speculate that reduced interface friction and high fluid pressures provided by fluid‐rich underplated sediment facilitates the tremor generation.