The 2016 Mw 6.5 Pidie Jaya, Aceh, North Sumatra, Earthquake: Reactivation of an Unidentified Sinistral Fault in a Region of Distributed Deformation

Abstract

On December 6, 2016, an Mw 6.5 earthquake occurred in Pidie Jaya, Aceh, about 30 km to the north of Sumatran Fault (SF) that killed more than 100 people Manuscript Click here to download Manuscript SRL_Muzli_etal_Manuscript_revised2.docx and destroyed approximately 3,000 buildings. Mainshock focal mechanism inversions using regional BMKG broadband data and teleseismic waveform data all indicate a strike-slip event with a centroid depth of 11-15 km. The observed macro intensity data show that most of the damaged buildings are distributed along the coast, approximately perpendicular to the ruptured fault strike instead of parallel with it. The strong shaking/damage sites are primarily located on the coastal sedimentary soils, highlighting the importance of site conditions in determining risk. We used one-month data recorded by nine temporal broadband stations to locate aftershocks with grid search and double-difference algorithms, thereby resolving a linear trend of seismicity aligned in NE-SW direction. The refined aftershock locations indicate a left-lateral rupture that is in agreement with the preliminary finite fault slip inversion as well as geomorphic signatures of local geological structure. Using a well-located ML 4.2 aftershock for path calibration,