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The 2018 Mw7.5 Palu ‘supershear’ earthquake ruptures geological fault’s multisegment separated by large bends: Results from integrating field measurements, LiDAR, swath bathymetry and seismic-reflection data
Natawidjaja D.H.a, Daryono M.R.a, Prasetya G.b, Udrekhc, Liu P.L.-F.d, Hananto N.D.a, Kongko W.e, Triyoso W.f, Puji A.R.a, Meilano I.f, Gunawan E.f, Supendi P.g, Pamumpuni A.f, Irsyam M.f, Faizal L.h, Hidayati S.i, Sapiie B.f, Kusuma M.A.f, Tawil S.j
a Indonesian Institute of Science, Indonesia
b Indonesian Association of Tsunami, Indonesia
c National Agency for Disaster Management (BNPB)
d National University of Singapore, Singapore
e Agency for the Assessments and Applications of Technology (BPPT)
f Institute of Technology Bandung, Bandung, Indonesia
g Agency for Meteorology, Climatology, and Geophysics (BMKG), Jakarta, Indonesia
h Ministry of Public Works and Housing, National Center for Earthquake Studies(PuSGeN), Bandung, Indonesia
i Geological Agency of Ministry of Mines and Energy, Center for Volcanology and Mitigation of Geological Disaster, Bandung, Indonesia
j Geology Department Palu, Tadulako University, Palu, Indonesia
[vc_row][vc_column][vc_row_inner][vc_column_inner][vc_separator css=”.vc_custom_1624529070653{padding-top: 30px !important;padding-bottom: 30px !important;}”][/vc_column_inner][/vc_row_inner][vc_row_inner layout=”boxed”][vc_column_inner width=”3/4″ css=”.vc_custom_1624695412187{border-right-width: 1px !important;border-right-color: #dddddd !important;border-right-style: solid !important;border-radius: 1px !important;}”][vc_empty_space][megatron_heading title=”Abstract” size=”size-sm” text_align=”text-left”][vc_column_text]© 2020 The Author(s) 2020. Published by Oxford University Press on behalf of The Royal Astronomical Society.On 2018 September 28, 18:02:44 local time, the magnitude 7.5 earthquake accompanied by a tsunami and massive liquefaction devastated Palu region in Central Sulawesi, Indonesia. Comprehensive post-disaster surveys have been conducted, including field survey of surface ruptures, LiDAR, multibeam-bathymetry mapping and seismic-reflection survey. We used these data to map fault ruptures and measure offsets accurately. In contrast to previous remote-sensing studies, suggesting that the earthquake broke an immature, hidden-unknown fault inland, our research shows that it occurred on the mappable, mature geological fault line offshore. The quake ruptured 177-km long multifault segments, bypassing two large releasing bends (first offshore and second inland). The rupture onset occurred at a large fault discontinuity underwater in a transition zone from regional extensional to compressional tectonic regimes. Then, it propagated southward along the ∼110-km submarine fault line before reaching the west side of Palu City. Hence, its long submarine ruptures might trigger massive underwater landslides and significantly contribute to tsunami generation in Palu Bay. The rupture continued inland for another 67 km, showing predominantly left-lateral strike-slip up to 6 m, accompanied by a 5-10 per cent dip-slip on average. The 7 km sizeable releasing bend results in a pull-apart Palu basin. Numerous normal faults occur along the eastern margin. They cut the Quaternary sediments, and some of them ruptured during the 2018 event. Our fault-rupture map on mature straight geological fault lines allows the possible occurrence of early and persistent ‘supershear’, but significant asperities and barriers on segment boundaries may prohibit it.[/vc_column_text][vc_empty_space][vc_separator css=”.vc_custom_1624528584150{padding-top: 25px !important;padding-bottom: 25px !important;}”][vc_empty_space][megatron_heading title=”Author keywords” size=”size-sm” text_align=”text-left”][vc_column_text]Compressional tectonics,Earthquake rupture,Multibeam bathymetry,Quaternary sediments,Seismic reflection data,Seismic reflection survey,Tsunami generation,Underwater landslides[/vc_column_text][vc_empty_space][vc_separator css=”.vc_custom_1624528584150{padding-top: 25px !important;padding-bottom: 25px !important;}”][vc_empty_space][megatron_heading title=”Indexed keywords” size=”size-sm” text_align=”text-left”][vc_column_text]Continental tectonics: strike-slip and transform,Earthquake hazards,Neotectonics,Paleoseismology,Submarine landslides,Tsunamis[/vc_column_text][vc_empty_space][vc_separator css=”.vc_custom_1624528584150{padding-top: 25px !important;padding-bottom: 25px !important;}”][vc_empty_space][megatron_heading title=”Funding details” size=”size-sm” text_align=”text-left”][vc_column_text]This study is funded by the CHL\R1\180173-GCRF grant from The Royal Society, UK. The fieldworks were supported and facilitated by The National Center for Earthquake study (PuSGeN), Japan International Cooperation Agency (JICA), the Ministry of Public Works, and Its Special Task Force for Palu Rehabilitation and Reconstructions, and the Central Sulawesi Province and Palu- City local governments. We are also grateful to The Agency of Geospatial Information (BIG) to develop and share the LiDAR data set. We thank all the Baruna Jaya 1 marine cruise crews and the NUS-IATsI team for their hard works and sharing the bathymetry data. We thank JICA for providing the seismic reflection data set and supporting the post-processing analysis. Finally, we appreciate Hiroyuki Tsutsumi and Timothy Henstock for their thorough and critical reviews in improving the manuscript. DHN is the main contributor in conceptualization, methodology, investigation, formal analysis, writing-original draft and visualization. MRD and ARP led the fault analysis based on field observations, LiDAR, orthophoto and bathymetry data, and assisted visualization. GP, PL, U and NDH conducted the multibeam bathymetry survey and provided the DEM data. WT conducted advanced processing and helped interpretations of the seismic-reflection data. PS conducted relocations of the 2018 pre-shocks, main shocks and aftershocks and provided the data. LF, MI and ST help organize and facilitate fieldwork. All authors participated in field surveys and contributed to developing and editing the manuscript.[/vc_column_text][vc_empty_space][vc_separator css=”.vc_custom_1624528584150{padding-top: 25px !important;padding-bottom: 25px !important;}”][vc_empty_space][megatron_heading title=”DOI” size=”size-sm” text_align=”text-left”][vc_column_text]https://doi.org/10.1093/gji/ggaa498[/vc_column_text][/vc_column_inner][vc_column_inner width=”1/4″][vc_column_text]Widget Plumx[/vc_column_text][/vc_column_inner][/vc_row_inner][/vc_column][/vc_row][vc_row][vc_column][vc_separator css=”.vc_custom_1624528584150{padding-top: 25px !important;padding-bottom: 25px !important;}”][/vc_column][/vc_row]