Seismic Microzonation and Liquefaction Potential Study by Using Microtremor Result Data in and Around Sipora Island, Indonesia

Geographically, the Mentawai Islands are located between two earthquake sources, and either of them could trigger a tsunami. In the eastern part of the Mentawai Islands, one earthquake source is the fault line along Sumatra. Mentawai Island had experienced some great earthquakes; the latest earthquake occurred in 2010 and produced a liquefaction event distributed along Sipora Island. This research proposes a seismic microzonation and liquefaction potential based on mictotermor observation results. We performed 53 microtremor single observations, and the observation sites were distributed across all districts with a population in Sipora Island, including north Sipora and south Sipora. The results show that the predominant period for mainland Tua Pejat in north Sipora and the whole of the south of Sipora Island (regions 1 and 3) have a large predominant period value >1 (long period), which indicates that the soil characteristic is soft soil. This result has correspondence with liquefaction potential Kg>5 while for the rock condition in region two the predominant period is less than 1s. These results provide crucial information for making seismic microzonation maps based on predominant period of soil and liquefaction potential map based on microtremor single observation, improving current hazard maps, and designing disaster prevention countermeasures in the north and south of Sipora Island, Indonesia.