Back-projection results for the M _w 7.5, 28 September 2018 Palu earthquake-tsunami

A back-projection technique allows seismologists to analyse rupture properties once seismic signals from a dense array of networks are available. The observed waveforms then traced back in space and time the source region an earthquake under investigation. In this study, method utilised image recorded high-frequency P -seismic filtered at 0.25-1.0 Hz by Multiple Signal Classification (MUSIC) processing estimate extent spread propagation M w 7.5 Palu event on 28 September 2018, generating severe tsunami. This study aims duration, its (the distance over which propagates) corresponding speed, directivity (where most energy propagates). results revealed that front propagates slightly offset southward about 2.9 km/s ~140 km away epicentre for 49 s before slowing down much smaller amplitudes after reaching south end Bay. finding is consistent with NNW-SSE orientation active Palu-Koro Fault lying along bay, suggesting strong ground motion associated fault activities. has therefore substantial implications enhanced tsunami early warnings, helping government local authority build community resilience warning people risk future possible hazards.