Basin and Crustal Structure of Jakarta and Bandung, Indonesia from Two Seismic Campaigns

Between October 2013 and February 2014, a dense portable seismic broadband network was operated by The Australian National University (ANU) and Indonesian Agency for Meteorology, Climatology and Geophysics (BMKG) in Jakarta, Indonesia. Jakarta is located in Java Island, Indonesia, with a population over 10 million. Overall 96 points were sampled through the successive deployments of 52 seismic broadband sensors at different parts of the city. After recording continuous seismic data for 5 months, the network was shifted to Bandung, another city to the south-east of Jakarta on March 2014. Bandung is situated on a old lake deposit surrounded by volcanic provinces. The configuration of the seismic network at Bandung encompasses the whole city as well as an active volcano-Tangkuban Perahu and Lembang Fault both located just outside of the city.

In both of the experiments, oceanic and anthropogenic noise were recorded as well as local and regional earthquakes. We apply regularized deconvolution to the recorded data of the vertical components of available station pairs, and over 4000 Green's functions were retrieved in total. Waveforms from stacked interstation deconvolutions show clear arrivals of Rayleigh and body waves. The traveltimes that were extracted from the group velocity filtering of Rayleigh wave arrivals, are used in a Transdimensional Bayesian seismic tomography method to map the velocity perturbations across cities. The constructed images at Jakarta mark the very low group velocities of Rayleigh waves, as low as 150 m/s at 1 Hz showing influence of a very low velocity basin. Low seismic velocity regions imaged through seismic noise tomography beneath both cities potentially posses a large risk of causing seismic amplification during a large earthquake close to the cities.