Rocky Mountain Section - 72nd Annual Meeting - 2020

Paper No. 2-10
Presentation Time: 11:35 AM


ASHCRAFT, Claire E.1, HARRIS, Ron A.2, REY, Kevin A.3, FRETHA, Julian4, SULAEMAN, Hanif2, PRASETYADI, Carolus5, PRADIPTA, Giovanni C.6, HANIFA, N. Rahma6, BELL, Ian R.2, WESTFALL, Ethan J.2, MANGUM, Abby L.2, WILLMORE, Rachel2 and BERRETT, Bryce E.2, (1)Department of Geological Sciences, Brigham Young University, S389 Eyring Science Center, Provo, UT 84602, (2)Department of Geological Sciences, Brigham Young University, S-389 ESC, Provo, UT 84602, (3)Department of Geological Sciences, Brigham Young University, Provo, UT 84602, (4)Disaster Mitigation Agency, Ambon, 84604, Indonesia, (5)Geology, Universitas Pembangunan Nasional, Jogjakarta, 84604, Indonesia, (6)Center of Excellence for Earthquake Science and Technology, Bandung Institute of Technology, Jl. Ganesha No.10, Lb. Siliwangi, Kecamatan Coblong, Kota Bandung, 40132, Indonesia

This multi-disciplinary investigation helps quantify the risk of natural hazards on the Indonesian islands of Lombok, Ambon, and Banda. In all three localities, MASW (multichannel analysis of surface waves) measurements were acquired to determine variations in Vs30 (shear-wave velocity to 30 meters depth). These measurements are used as a proxy for likely earthquake shaking intensity (MMI). We test the correlation between these values and MMI variations estimated from modern and historical earthquakes with the goal of mapping shaking susceptibility by area. These areas have suffered casualties and damage from multiple large earthquakes, both historical and as recent as 2019.

The Banda Islands, which are surrounded by 270º of subduction zones, offer historical data regarding 400 years of earthquakes and associated tsunamis. One of the best-documented earthquake and tsunami events occurred in 1852. A new methodology involving Bayesian statistical inversion is used to reconstruct the most likely source parameters of this event. This method may also be applied to forecast earthquake and tsunami risks from other historical events worldwide.

Our investigation of Banda Api volcano over a 6-year time span revealed an active normal fault scarp that cuts through the summit. The last eruption in 1988 extruded lava flows from the fault zone along the flanks of the volcano, delineating a zone of weakness along which a future sector collapse may occur. A numerical simulation of this event produces a tsunami with up to 76 meters of run-up that inundates nearly every human-occupied part of the islands. The same methodology is used to reconstruct a landslide tsunami that occurred on the north coast of Ambon in 1674 with a 100 meter of run up.

Our work also involves community outreach in these areas to improve local geohazard education and preparedness.