Seminar: Seismic Tomographic Imaging: Applications to the Subduction Zone beneath Sumatra and the Shallow Crustal Structure in Java

by Dr. Sri Widiyantoro, Professor, Institute of Technology Bandung, Indonesia

Friday 10 May 2019, 11AM – 12PM, ARRC Auditorium

ABSTRACT: Seismic tomographic imaging has been successfully applied to improve P-wave velocity structure beneath Sumatra using the new data provided by the 2004–2005 Sumatra-Andaman great earthquake sequences and a non-linear approach. Nearly one million compressional phases from events within the Indonesian region have been used. These include the surface-reflected depth phases pP and pwP in order to increase the sampling of the upper-mantle structure, particularly below the back-arc regions. We have combined a high-resolution regional inversion with a low-resolution global inversion to minimise the mapping of distant aspherical mantle structure into the study region. The tomographic images indicate that the slab is folded at depth beneath northern Sumatra, exhibiting geometry similar to that of the volcanic arc and the trench at the surface. We interpret that this fold plays a major role in the segmentation of the Sumatra megathrust, and may impede rupture propagation in the region.

In addition, several applications of seismic tomographic imaging on a local scale in Java will also be presented. These include volcano tomography and the ambient noise tomography (ANT) of megacities, such as Jakarta and Bandung, which have tall buildings built on basins filled with poorly consolidated sediments. The ANT results provide an estimate of the thickness and shear velocity of the basin fill, which is critical to understanding seismic hazard because of the potential for amplification and resonance of seismic waves.

BIOGRAPHY: Sri Widiyantoro is a professor of seismology at ITB, Bandung, Indonesia, where he has spent his academic career since 1987. He conducted research and study visits at prestigious universities overseas, including MIT and ANU, where he finished his PhD program, and research institutions (e.g. Earthquake Research Institute, Tokyo University) to work with top scientists on collaborative research. His main research interest is in the field of seismology, particularly seismic tomographic imaging. His tomographic models were published in various journals, including top journals like Science and Nature. Alongside his work on large-scale seismological problems, he has engaged actively in consultancy on oil, gas, and geothermal explorations related work in Indonesia, so that he can bring a broad perspective to his science.

He has received recognition through many awards including the Doornbos Memorial Prize from IUGG, the Habibie Award from the Habibie Center, the Science and Technology Award from the Indonesian Toray Science Foundation, the Australian Alumni Award for Research and Innovation from the Embassy of Australia in Jakarta, and the Sarwono Award from the Indonesian Institute of Sciences (LIPI). He has been a Fellow of the Indonesian Academy of Sciences since 2011. He is currently Dean of Faculty of Mining and Petroleum Engineering, ITB (from 2011), and was President for the Indonesian Association of Geophysicists (2012-2014).