Detailed seismic imaging of Merapi volcano, Indonesia, from local earthquake travel-time tomography

Ramdhan, Mohamad; Widiyantoro, Sri; Nugraha, Andri Dian; Métaxian, Jean-Philippe; Rawlinson, Nicholas; Saepuloh, Asep; Kristyawan, Said; Sembiring, Andry Syaly; Budi-Santoso, Agus; Laurin, Antoine; Fahmi, Ahmad Ali

doi:10.1016/j.jseaes.2019.03.018

Cited by 27 publications

(15 citation statements)

References 32 publications

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“…However, we also detected a near-vertical cluster of events that may be related to a backthrust, as has been found in other locations, e.g. in Sumatra (Pesicek et al 2010) and in Central Java (Ramdhan et al 2019). A backthrust occurs as a result of layer-parallel shortening in a late stage of thrust sequences in which it is displaced in an opposite direction to that of the main thrust direction (Xu et al 2015).…”

Section: Resultssupporting

confidence: 84%

Potential megathrust earthquakes and tsunamis off the southern coast of West Java, Indonesia

Supendi

Widiyantoro

Muhari³

et al. 2020

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High seismicity rates in and around West Java occur as a result of the Indo-Australian plate converging with and subducting beneath the Sunda plate. Large megathrust events associated with this process likely pose a major earthquake and tsunami hazard to the surrounding community, but further effort is required to help understand both the likelihood and frequency of such events. With this in mind, we exploit catalog and phase data sourced from the Agency for Meteorology, Climatology, and Geophysics (BMKG) of Indonesia and the International Seismological Centre (ISC) for the period of April 2009 through July 2020, in order to conduct earthquake hypocenter relocation using a teleseismic double-difference method. Our results reveal a seismic gap to the south of West Java, which is in agreement with a previous GPS study that finds the same region to be a potential future source of megathrust earthquakes. Tsunami modeling was conducted in the region based on two scenarios using sources from the Indonesian National Center for Earthquake Studies, and show that the maximum tsunami height may be up to ~ 8 m. This estimate is approximately half the maximum tsunami height predicted by a previous study in which earthquake sources were derived from GPS data inversion.

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Section: Resultssupporting

confidence: 84%

Potential megathrust earthquakes and tsunamis off the southern coast of West Java, Indonesia

Supendi

Widiyantoro

Muhari³

et al. 2020

Preprint

Self Cite

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“…• C (i.e., Sebau, Kukusan, Kalak, Segara Anakan I, Segara Anakan II, Segara Anakan III, and Segara Anakan IV) (Sundhoro et al, 2000;Hadi et al, 2007). Based on the velocity and attenuation characteristics and also an indication of high temperature, this region might contain fluids: either high temperature water-filled or melts (Nakajima and Hasegawa, 2006;Ramdhan et al, 2019). We suggest that the dense fractures at a depth of ∼ 0-20 km with high permeability may be the pathway for hot water to rise to the surface.…”

Section: Other Geological Featuresmentioning

confidence: 99%

Seismic Attenuation Tomography From 2018 Lombok Earthquakes, Indonesia

et al. 2021

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Local earthquake data was used to determine a three-dimensional (3D) seismic attenuation structure around the aftershock source region of the 2018 Lombok earthquake in Indonesia. The aftershocks were recorded by 13 seismic stations from August 4 to September 9, 2018. The selected data consist of 6,281 P-wave t∗ values from 914 events, which had good t∗ quality in at least four stations. Our results show that the two aftershock clusters northwest and northeast of Lombok Island have different attenuation characteristics. A low P-wave quality factor (low-Qp), low P-wave velocity (Vp), and high ratio of P-wave velocity and S-wave velocity (Vp/Vs), which coincide with a shallower earthquake (<20 km) northwest of Lombok Island, might be associated with a brittle area of basal and imbricated faults influenced by high fluid content. At the same time, the high-Qp, low Vp, and low Vp/Vs, which coincide with a deeper earthquake (>20 km) northeast of Lombok Island, might be associated with an area that lacks fluid content. The difference in fluid content between the northwest and northeast regions might be the cause of the early generation of aftershocks in the northwest area. The significant earthquake that happened on August 5, 2018, took place in a region with moderate Qp, close to the contrast of high and low-Qp and high Vp, which suggests that the earthquake started in a strong material before triggering the shallower aftershocks occurring in an area affected by fluid content. We also identified an old intrusive body on the northeast flank of the Rinjani volcano, which was characterized by a high-Qp, high-velocity, and a high Bouguer anomaly.

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“…On local scales, previous studies have been used to study small-scale structures of crust and upper mantle i.e., fault zones and volcanism. They observed strong low-velocity anomalies beneath volcanoes in Central Java (Koulakov et al, 2007(Koulakov et al, , 2016Wagner et al, 2007;Bohm et al, 2013;Luehr et al, 2013;Rohadi et al, 2013;Haberland et al, 2014;Zulfakriza et al, 2014;Ramdhan et al, 2019). They have found an extreme lowvelocity anomaly in the crust beneath Merapi and Lawu volcanoes (Merapi-Lawu anomaly (MLA)) with a high Vp/Vs ratio of 1.9.…”

Section: Introductionmentioning

confidence: 99%

Seismic Imaging of Lithospheric Structure Beneath Central-East Java Region, Indonesia: Relation to Recent Earthquakes

et al. 2022

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The Central and East Java region, which is part of the Sunda Arc, has an important role in producing destructive earthquakes and volcanic complexes in Indonesia as a result of the convergence between the Indo-Australian plate that subducts under the Eurasian plate. In this study, the 3-D seismic velocity structure (Vp, Vs, and Vp/Vs) of the crust and upper mantle was determined to reveal the presence of the subducted slab, volcanic sources, and seismogenic features in the Central and East Java region. We have manually re-picked P- and S-arrivals of 1,488 events from January 2009 to September 2017 recorded at 27 stations of the BMKG network. An iterative damped least-squares inversion method was applied to simultaneously calculate both hypocenter relocations and velocity structure beneath this high-risk region to a depth of 200 km. We then compare the tomographic results and seismicity to interpret structural features in the seismic zones. The subducted slab is dipping toward the north, imaged by the high-velocity regions with low Vp/Vs at depths of about 50–100 km. Low-velocity anomalies with high Vp/Vs above the slab at a depth of ∼100 km, imply the possible location of partial melting from slab dehydration. Fluids and melts are ascending to feed the volcanoes i. e., Merapi-Merbabu, Wilis, Pandan, Semeru, Bromo, and Ijen that also have similar low-velocity anomalies at 10–30 km depths, suggesting the presence of the sedimentary basin or magma reservoir. We also have redetermined the hypocenter location of the 2021 (Mw 6.1) Malang earthquake at 8.94oS, 112.45oE, with a depth of 59.7 km. The location error in the x, y, and z directions are 3.08, 6.39, and 11.91 km, respectively. This intraslab event with a thrusting mechanism is located in the high-velocity region and close to the intermediate-depth seismic clusters, which indicates the geometry of the oceanic slab. In the region of 1994 (Mw 7.8) Banyuwangi earthquake, we found a low-velocity anomaly at ∼ 50 km depth that might be associated with the presence of subducting seamount that is more hydrated than the surrounding slab. The slip over this subducting seamount caused the tsunamigenic earthquake.

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Detailed seismic imaging of Merapi volcano, Indonesia, from local earthquake travel-time tomography

Cited by 27 publications

References 32 publications

Potential megathrust earthquakes and tsunamis off the southern coast of West Java, Indonesia

Potential megathrust earthquakes and tsunamis off the southern coast of West Java, Indonesia

Seismic Attenuation Tomography From 2018 Lombok Earthquakes, Indonesia

Seismic Imaging of Lithospheric Structure Beneath Central-East Java Region, Indonesia: Relation to Recent Earthquakes

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