An Integrated Analysis of Seismic and InSAR data from the June 2012 Koa‘e Fault System Earthquake Sequence, Hawai‘i

Abstract:

The Koa‘e fault system is a prominent but poorly understood structural element of Kilauea Volcano, Hawai‘i. The ~E-W-trending normal faults that make up the Koa‘e system are located about 5 km south of the summit caldera and extend between the East and Southwest Rift Zones, providing a means of accommodating both magma transport between the rifts and extension due to seaward motion of the volcano’s south flank. On 5 June 2012, a sequence of shallow earthquakes with magnitudes up to M3.6 occurred within the central part of the Koa‘e fault system. InSAR data from multiple satellites spanning the time of the earthquakes indicates a maximum of about 10 cm of down-to-the-north displacement on a known Koa‘e fault. Field visits to the fault after the earthquakes found abundant ground cracking. Here, we combine the InSAR data acquired by the COSMO-SkyMed, TSX and RSAT2 systems and seismic data recorded by the Hawaiian Volcanology Observatory to analyze the characteristics of fault rupture. High-precision earthquake locations of the 2012 sequence together with the background seismicity that extends back to 1986 are obtained by applying three-dimensional ray-tracing, similar-event cluster analysis, and waveform cross-correlation methods. The integrated analysis is helpful to better constrain the geometry of the fault, its depth extent, and its role in the structural evolution of Kilauea.