Remotely triggered nonvolcanic tremor in Sumbawa, Indonesia

Abstract

We present, for the first time, evidence for triggered tremor beneath the island of Sumbawa, Indonesia. We show triggered tremor in response to three teleseismic earthquakes: the Mw 9.0 2011 Tohoku earthquake and two oceanic strike-slip earthquakes (Mw 8.6 and Mw 8.2) offshore of Sumatra in 2012. We constrain an apparent triggering threshold of 1 mm/s ground velocity that corresponds to about 8 kPa dynamic stress. Peak tremor amplitudes of about 180 nm/s are observed, and scale with the ground velocity induced by the remote earthquakes. Triggered tremor responds to 45-65 s period surface waves and predominantly correlates with Rayleigh waves, even though the 2012 oceanic events have stronger Love wave amplitudes. We could not locate the tremor because of minimal station coverage, but data indicate several potential source volumes including the Flores Thrust, the Java subduction zone, or Tambora volcano.