A tsunami generated by a strike-slip event.: constraints from GPS and SAR data on the 2018 Palu earthquake
Simons, Wim J.F.; Broerse, Taco; Shen, Lin; Kleptsova, Olga; Nijholt, Nicolai; Hooper, Andrew; Pietrzak, Julie; Morishita, Yu; Naeije, Marc; Lhermitte, Stef; Herman, Matthew; Sarsito, D.A.; Efendi, Joni; Sofian; Govers, Rob; Vigny, C.; Abidin, Hasanuddin; Pramono, Gatot Haryo; Nugroho, Cahyo; Visser, Pieter; Riva, Riccardo
(2022) Journal of Geophysical Research: Solid Earth, volume 127, issue 12
(Article)
Abstract
A devastating tsunami struck Palu Bay in the wake of the 28 September 2018 Mw = 7.5 Palu earthquake (Sulawesi, Indonesia). With a predominantly strike-slip mechanism, the question remains whether this unexpected tsunami was generated by the earthquake itself, or rather by earthquake-induced landslides. In this study we examine the tsunami potential
... read more
of the co-seismic deformation. To this end, we present a novel geodetic data set of Global Positioning System and multiple Synthetic Aperture Radar-derived displacement fields to estimate a 3D co-seismic surface deformation field. The data reveal a number of fault bends, conforming to our interpretation of the tectonic setting as a transtensional basin. Using a Bayesian framework, we provide robust finite fault solutions of the co-seismic slip distribution, incorporating several scenarios of tectonically feasible fault orientations below the bay. These finite fault scenarios involve large co-seismic uplift (>2 m) below the bay due to thrusting on a restraining fault bend that connects the offshore continuation of two parallel onshore fault segments. With the co-seismic displacement estimates as input we simulate a number of tsunami cases. For most locations for which video-derived tsunami waveforms are available our models provide a qualitative fit to leading wave arrival times and polarity. The modeled tsunamis explain most of the observed runup. We conclude that co-seismic deformation was the main driver behind the tsunami that followed the Palu earthquake. Our unique geodetic data set constrains vertical motions of the sea floor, and sheds new light on the tsunamigenesis of strike-slip faults in transtensional basins.
show less
Download/Full Text
Keywords: GPS, InSAR, Palu Bay tsunami, Palu earthquake, fault bend, transtension, Geophysics, Geochemistry and Petrology, Earth and Planetary Sciences (miscellaneous), Space and Planetary Science
ISSN: 2169-9313
Publisher: Wiley
Note: Funding Information: Some specifications to the CReDiT contributions. Data curation concerns collecting GPS data and maintaining the GPS network. For the formal analysis, W.S. has processed the GPS data and Y.M. has performed the SAR-data processing; W.S. and M.N. combined bathymetric and topographic data. T.B. has led the investigation process and has combined the different co-seismic displacement datasets into the combined displacement field; L.S. has conducted the finite fault inversion; O.K. has performed the tsunami modeling; N.N. has analyzed the fault directions; S.L. has analyzed the inundation on basis of optical data. T.B. has taken lead in writing the manuscript, supported by N.N. The continued (long-term) operation of the GPS stations in Central Sulawesi has been co-facilitated by the EU-ASEAN SEAMERGES (2004–2006) and GEO2TECDI-1/2 projects (2009–2013). The GPS data acquisition and research were also partly funded by grants from the Dutch NWO User Support Programme Space Research (2007–2023). A special thanks to our local survey staff Rahman Umar and Urip for their continued support, including the inspection of the GPS stations directly after the earthquake. ALOS-2 data were provided under a cooperative research contract between GSI and JAXA. The ownership of ALOS-2 data belongs to JAXA. Taco Broerse is funded by NWO grant ALWGO.2018.038. Olga Kleptsova was initially funded by a 2 months PD grant awarded to J. Pietrzak by the Department of Hydraulic Engineering, TU Delft which is gratefully acknowledged. Matthew Herman was funded by The Netherlands Research Centre For Integrated Solid Earth Science, grant ISES 2017-UU-22. COMET is the UK Natural Environment Research Council's Centre for the Observation and Modelling of Earthquakes, Volcanoes and Tectonics. We would like to dedicate our research work in memory of all casualties of the 2018 Palu earthquake. This includes Maya Pasau, who helped us with setting up one of the GNSS stations, her husband Yudi and their children Fiki and Al who tragically lost their lives when the tsunami struck Talise beach. Furthermore, we thank Jeffrey Freymueller, two anonymous reviewers, editor Isabelle Manighetti and associate editor Alice-Agnes Gabriel for their helpful reviews and suggestions to improve the manuscript. Funding Information: Some specifications to the CReDiT contributions. Data curation concerns collecting GPS data and maintaining the GPS network. For the formal analysis, W.S. has processed the GPS data and Y.M. has performed the SAR‐data processing; W.S. and M.N. combined bathymetric and topographic data. T.B. has led the investigation process and has combined the different co‐seismic displacement datasets into the combined displacement field; L.S. has conducted the finite fault inversion; O.K. has performed the tsunami modeling; N.N. has analyzed the fault directions; S.L. has analyzed the inundation on basis of optical data. T.B. has taken lead in writing the manuscript, supported by N.N. The continued (long‐term) operation of the GPS stations in Central Sulawesi has been co‐facilitated by the EU‐ASEAN SEAMERGES (2004–2006) and GEO2TECDI‐1/2 projects (2009–2013). The GPS data acquisition and research were also partly funded by grants from the Dutch NWO User Support Programme Space Research (2007–2023). A special thanks to our local survey staff Rahman Umar and Urip for their continued support, including the inspection of the GPS stations directly after the earthquake. ALOS‐2 data were provided under a cooperative research contract between GSI and JAXA. The ownership of ALOS‐2 data belongs to JAXA. Taco Broerse is funded by NWO grant ALWGO.2018.038. Olga Kleptsova was initially funded by a 2 months PD grant awarded to J. Pietrzak by the Department of Hydraulic Engineering, TU Delft which is gratefully acknowledged. Matthew Herman was funded by The Netherlands Research Centre For Integrated Solid Earth Science, grant ISES 2017‐UU‐22. COMET is the UK Natural Environment Research Council's Centre for the Observation and Modelling of Earthquakes, Volcanoes and Tectonics. We would like to dedicate our research work in memory of all casualties of the 2018 Palu earthquake. This includes Maya Pasau, who helped us with setting up one of the GNSS stations, her husband Yudi and their children Fiki and Al who tragically lost their lives when the tsunami struck Talise beach. Furthermore, we thank Jeffrey Freymueller, two anonymous reviewers, editor Isabelle Manighetti and associate editor Alice‐Agnes Gabriel for their helpful reviews and suggestions to improve the manuscript. Publisher Copyright: © 2022 The Authors.
(Peer reviewed)
