The Kalaotoa Fault: A Newly Identified Fault that Generated the Mw 7.3 Flores Sea Earthquake

Supendi, Pepen; Rawlinson, Nicholas; Prayitno, Bambang; Widiyantoro, Sri; Simanjuntak, Andrean V. H.; Palgunadi, Kadek Hendrawan; Kurniawan, Andri; Marliyani, Gayatri Indah; Nugraha, Andri Dian; Daryono, Daryono; Anugrah, Suci Dewi; Fatchurochman, Iman; Gunawan, Mohammad Taufik; Sadly, Muhammad; Adi, Suko Prayitno; Karnawati, Dwikorita; Arimuko, Abraham

doi:10.1785/0320220015

Cited by 13 publications

(16 citation statements)

References 24 publications

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“…The study about detailed structure for unknown fault is still limited in the Indonesia region. Recently, Muksin et al [13] found the backthrust in the northern part of Sumatra and Supendi et al [14] found the responsible fault for Mw 7.8 in the Flores Sea in 2021. However, this is the first study that conducted in the Toba region to learn the swarm evidence.…”

Section: Resultsmentioning

confidence: 99%

Preliminary Result of Swarm Activities in Toba Region Using Dense Temporary Network

Nadia,

Simanjuntak,

Arifullah

et al. 2023

IOP Conf. Ser.: Earth Environ. Sci.

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For the first time, an earthquake swarm occurred in 2021 in Lake Toba (Indonesia), one of the largest calderas in the world. Although the earthquakes were located in the volcanic environment, the swarm activities could be related to the tectonic activities from the Sumatra fault system. The swarm activities occurred at a very shallow depth and were felt with the intensity of II–IV MMI by local people. The objective of this research was to investigate the characteristics of the earthquake swarm in the Toba Caldera from the waveforms recorded by temporary stations in March – June 2021. A total of 26 seismic stations were deployed for two months in May and June 2021. Automatic detection of seismic waves is important because it can be used for earthquake early warning systems and speeds up analysis of origin time, P-, and S arrival times, and earthquake locations. We found characteristics of spectrum waveform from low to high frequency of a non-swarm earthquake, while high frequency seismograms were generated by the swarm earthquake. Furthermore, we successfully captured the hypocentre that was distributed in the SW – NE direction and may figure out the unknown geological system that is responsible for the swarm activities.

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Section: Resultsmentioning

confidence: 99%

Preliminary Result of Swarm Activities in Toba Region Using Dense Temporary Network

Nadia,

Simanjuntak,

Arifullah

et al. 2023

IOP Conf. Ser.: Earth Environ. Sci.

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“…Fault structures and tectonic lineaments are recorded and can be interpreted through remote sensing imagery (e.g., satellite imagery, digital terrain model, and/or shuttle radar topography mission). The entire geological structure of Kalaotoa Island was formed at the beginning of the Middle Miocene and its peak at the time of the Pliocene -Pleistocene (Koswara et al, 1994;Supendi et al, 2022). Koswara et al, 1994)…”

Section: Geological Settingmentioning

confidence: 99%

“…10). The seismicity and tectonics of the Flores Sea thrust system (FSTS) consisting of the Flores Sea thrust, Selayar fault, and Kalaotoa fault have been reported by several researchers (e.g., Goes et al, 1997;Hall & Sevastjanova, 2012;Hutchings & Mooney, 2021;Supendi et al, 2020Supendi et al, , 2022Yang et al, 2020) This reverse fault once triggered an earthquake of MW 7.8 at a depth of 27.7 km and triggered a tsunami wave as high as 25 m with a distribution radius of 300 m on 12/12/1992, at 01:29 pm.…”

Section: Introductionmentioning

confidence: 97%

“…Epicenters of moderate and large events (MW 4-8) that occurred in shallow depth (<800 km) from 1962 to 2021 are shown. Magnitude source: Hutchings & Mooney, 2021; Supendi et al, 2020, 2022; Yang et al, 2020; and Indonesian Earthquake Catalog, the based map: peak ground acceleration (PGA) by USGS (2021).Structural lineaments are drawn after(Koswara et al, 1994 ;Supendi et al, 2022)…”

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confidence: 99%

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Lineament Density and Implications for the Distribution of Ground Fissures After 2021 MW 7.3 Flores Sea Earthquake on Kalaotoa Island, Indonesia

Maulana

Burhanuddin

Akbar

2023

J. Geoscience Eng. Environ. Technol.

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A 7.3 MW earthquake occurred at 11:20 am on December 14, 2021, in the Flores Sea, and the main shake was centered ±100 km north of Maumere, Indonesia, with a depth of 14.3 km, antecedent a landslide. This research consists of two stages, namely: quantitative data collection in the form of tectonic lineament density measurements using Shuttle Radar Topography Mission (SRTM) data which is extracted manually using GIS-based applications, and qualitative data in the form of field observations which include strike-dip measurements of rocks, lithological data, morphological conditions, ground fissures, and the distribution of damage caused after 2021 earthquake. This study focused on analyzing the value of lineament density, its correlation to the history of seismicity and surface lithological conditions, and the impact after the 2021 earthquake damage. The lineaments of the southern area are dominated by NE – SW orientation along with various lithological conditions and with lineament density values very low – very high. A crack width from 0.5 to 112 cm, and a vertical offset occurs with a depth of up to 270 cm. The western area is dominated by lineament with an orientation NE – SW with a crack width from 8 to 18 cm, and there is a vertical offset with a depth of up to 24 cm. The distribution of ground fissures in the Garaupa Raya area is categorized as low. The orientation of the northern area lineament is relatively NW – SE directional and the lineament density value is categorized as low. Horizontal displacement with an orientation of NW – SE is found at the port of Kalaotoa Island, Kawawo village with measured crack width of ±17 cm, an observable horizontal offset from 15 to 24 cm, and a vertical offset of ±12 cm with a trend of movement towards the south.

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“…Use of seismic stress change analysis has been demonstrated by studying earthquake activity in order to assess seismic and tsunami hazards on faults, i.e., strike-slip [21]- [23], normal [24]- [26], and collusion [27]. However, the seismic stress changes in subduction and intraplate earthquakes, especially in complex systems, and their potential effects on regional seismic activity, have not been comprehensively investigated.…”

Section: Introductionmentioning

confidence: 99%

Analysis of Change of Seismic Stress Along the Sumatran Zone to Predict Potential Earthquake Zones

Jihad¹

2023

GEOMATE

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A seismic stress change analysis is a powerful method to investigate the relationship of earthquakes, sequences, aftershocks, and potential seismic zones. In previous studies, the analysis was demonstrated by studying earthquake activity to assess seismic hazards on strike-slip, normal, and collisional thrust faults. Unfortunately, seismic stress changes in complex systems, such as subduction and intraplate earthquakes, have not been fully observed, to our knowledge. The objective of the research is to investigate seismic stress changes and their potential effects on the Sumatra subduction zone by using Colomb Stress Change Analysis (Colomb 3.3). The investigation is focused on high-accuracy major earthquake events, during the period of 2004 to 2019, and 50 major earthquakes within a period of 15 years are taken into account to investigate potential zones. Different from previous work, we included temporal and spatial analysis in order to estimate possible future significant seismic events. The results show that the 2004 Aceh-Andaman earthquake triggered the 2005 Nias earthquake as also suggested by previous study. Meanwhile, the 2008 earthquake (Mw 7.2) triggered the Padang earthquake (2009). Our new finding suggests that the 2008 earthquake also provided a positive impulse for the 2010 Mentawai earthquake. Several potential earthquake zones are found at depths of 20 to 50 km in Bengkulu, of 60 to 80 km in Mentawai. The results of this study can be a key to understanding the probability of seismic and tsunami hazards in Sumatra, which is also applicable to other potentially hazardous areas in Indonesia.

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The Kalaotoa Fault: A Newly Identified Fault that Generated the Mw 7.3 Flores Sea Earthquake

Cited by 13 publications

References 24 publications

Preliminary Result of Swarm Activities in Toba Region Using Dense Temporary Network

Preliminary Result of Swarm Activities in Toba Region Using Dense Temporary Network

Lineament Density and Implications for the Distribution of Ground Fissures After 2021 MW 7.3 Flores Sea Earthquake on Kalaotoa Island, Indonesia

Analysis of Change of Seismic Stress Along the Sumatran Zone to Predict Potential Earthquake Zones

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