ORCID Profile
0000-0002-4232-6514
Current Organisations
Australian National University
,
University of Adelaide
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Publisher: Copernicus GmbH
Date: 27-03-2022
DOI: 10.5194/EGUSPHERE-EGU22-3579
Abstract: & & Rinjani volcano is a highly active volcano located on Lombok Island in eastern Indonesia which has experienced ten eruptions in the last 100 years. Between 2014 and 2020, this stratovolcano has erupted twice, on 25& sup& th& /sup& October 2015 and on 1st August 2016. Both eruptions lasted approximately two months, with activity concentrated in the volcanoes central Barujari Crater region. In 2018, four deadly (Mw 6.2 to 6.9) earthquakes struck the north coast of Lombok Island on 28& sup& th& /sup& July, 5& sup& th& /sup& August, and 19& sup& th& /sup& August, causing hundreds of fatalities and extensive damage. These earthquakes also resulted in the remobilization of ash deposits on the flanks of Rinjani volcano located on the north island as landslides. Our InSAR-based finite fault rupture modelling suggests the estimated maximum fault slip of 1.4 m, 2.3 m, and 2.5 m for the three mainshocks located on southward dipping fault planes to the northwest-northeast of the Rinjani volcano occurred at depths of ~15 km, 12 km, and 32 km, respectively. Coulomb stress change modelling based on the these rupture models indicates about 1 MPa of extensional stress change at 10 to 20 km of depth around the crater region was observed, which may promote opening of the magma conduit. The short distance between the peak slip region and the volcano, as well as the stress change, raises the question of whether the earthquake sequence may have influenced the spatio-temporal deformation pattern of the Rinjani volcano.We use an InSAR time-series, consisting of 658 descending and 370 ascending Sentinal-1 interferograms to investigate the time-dependent inflation and deflation signals around the crater region generated by the 2015, 2016 eruptions and the 2018 earthquakes. We analyse the average inflation/deflation rate and the cumulative displacements in different periods between 2014 and 2020 to quantify the volcano deformation before and after the 2018 earthquake sequence. Our preliminary results reveal that the crater region has undergone rapid inflation of up to 20 mm/yr through the 2014 to 2017 period, before significantly slowing to ~10 mm/yr over the 2017 to 2018 period. During the first three months following the 2018 earthquake sequence, a noticeable deflation of the edifice was detected, followed by gentle inflation lasting until late 2020. These results imply that the influence of the 2018 earthquakes acted to reduce the pressure in the reservoir, at least temporarily. We will present results from modelling the volume change and the location of the volcano pressure source for better understanding how changes in the magma body and magma movement may have been influenced by the 2018 Lombok earthquake sequence.& &
Publisher: Copernicus GmbH
Date: 15-05-2023
DOI: 10.5194/EGUSPHERE-EGU23-13534
Abstract: In 2018, four deadly (Mw 6.2 to 6.9) earthquakes struck the north coast of Lombok Island, on 28 July, 5August, and 19 August, distributed between the Flores back-arc thrust and the Rinjani-Samalas volcanic complex, causing hundreds of fatalities and extensive damage. We performed a comprehensive analysis of relocated aftershocks, static coulomb stress changes, and co-seismic and post-seismic deformation, to improve our understanding of this earthquake sequence. The fault geometries and slip distributions of the three mainshocks are modelled by inverting the co-seismic deformation imaged using an interferometric analysis of Sentinel-1 synthetic aperture radar (InSAR) measurements, based on rectangular dislocations embedded in a multi-layered elastic half-space. The earthquake sequence aftershocks were analysed using an unsupervised learning method (ST-DBSCAN) to cluster these relocated aftershocks so that we can identify the source of each aftershock. We used a time-series consisting of 658 descending and 370 ascending Sentinal-1 InSAR interferograms to investigate the time-dependent post-seismic deformation in the two years following the Lombok 2018 earthquake sequence, deriving a combined model that simulates the viscoelastic relaxation and afterslip simultaneously. The Coulomb stress change modelling based on the co-seismic and post-seismic rupture models indicates about 1 MPa of extensional stress change at 10 to 20 km of depth and 0.5 Mpa extensional stress change at 15 to 25 km of depth around the Barujari Crater region, respectively, which affects the open of the magma conduct, reflected as caldera-scale deflation and inflation. To quantify the influence of the earthquake sequence on the spatiotemporal deformation pattern of the volcano edifice, we extended our InSAR time-series range forward to the year 2014, just prior to the two eruptions that occurred on 25th October 2015 and 1st August 2016, and perform Principal Component Analysis to investigate the time-dependent inflation and deflation signals. We modelled the volume change and the location of the volcano pressure source for a better understanding of how changes in the magma body and magma movement may have been influenced by the 2018 Lombok earthquake sequence. A double-source compound model is used to invert the parameters of the magma chamber, including a shallow Moji point pressure source centred at 1.3 km north of the Barujari cone, and a deep source centred at 1.5 km northeast of the Rinjani cone, at ~3.9 km and ~3.5 km depth below the sea level respectively. We also used a uniform sill and dike combined model to interpret the co-eruptive signals surrounding the observed eruptive fissures. Our best-fit dike is nearly vertical, reaching a depth of 2 km below sea level with an opening of 8.5 cm, and the sill is at the depth of 3.1 km with a contraction of 40 cm.
Publisher: Springer Science and Business Media LLC
Date: 02-03-2020
Publisher: American Geophysical Union (AGU)
Date: 02-2023
DOI: 10.1029/2022JB024810
Abstract: The Indonesia‐Australia‐New Guinea collision zone comprises a complex system of tectonic blocks whose relative motion accommodates convergence of the Sunda Block, Pacific, Australian, and Philippine Sea plates. Previous studies have considered either the western or eastern ends of this system, in eastern Indonesia and Papua New Guinea, respectively. However, these studies had limited ability to characterize either the kinematics of the central part of the system or transitions in tectonic regime across it. In this study, we perform a simultaneous inversion of 492 earthquake slip vectors and 267 GPS velocities to quantify the block movement spanning the Sunda‐Banda Arc, Western New Guinea, and Papua New Guinea. Our best‐fitting kinematic block model comprises 23 elastic blocks, for which we estimate the rotation rates and block boundary slip rates. We show how the Cenderawasih Bay sphenochasm was likely formed by a combination of both rotations (2.82 ± 0.11°/Myr anticlockwise) of the Bird's Head Block and southwest‐directed convergence (39.9 ± 1.7 mm/yr) along the Lowlands fault. Our estimated relative slip vectors across the New Guinea Fold‐and‐Thrust Belt indicate a transition in the tectonic regime of the block boundary from predominately thrust faulting at its western segment, with a convergence rate up to 19.5 ± 0.6 mm/yr, to predominately sinistral motion in the center segment with slip rate ∼7 mm/yr, and returning to thrust in the eastern segment with a convergence rate up to 9.0 ± 0.5 mm/yr, implying the combined effect of multiple driving mechanisms.
Publisher: Geological Society of London
Date: 30-05-2020
No related grants have been discovered for Siyuan Zhao.