The new insight of tectonic setting in Sunda–Banda transition zone using tomography seismic. Case study: 7.1 M deep earthquake 29 August 2023

Mia Uswatun Hasanah; Pepen Supendi; Andri Dian Nugraha; Sri Widiyantoro; Firman Syaifuddin

doi:10.1515/geo-2022-0710

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The new insight of tectonic setting in Sunda–Banda transition zone using tomography seismic. Case study: 7.1 M deep earthquake 29 August 2023

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Veröffentlicht/Copyright: 9. November 2024

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Abstract

The Sunda–Banda arc transition zone features the collision of the Indo-Australian oceanic plate and the Australian continent, resulting in intricate geological and geodynamic conditions. Tectonic activity in this region is shaped by the convergence of multiple major plates, including the Indo-Australian oceanic plate and the Eurasian plate. The crustal structure along the Sunda–Banda arc transition zone is complex and influenced by various factors such as subduction, continental collision, and volcanic activity. The tectonic complexity of the region in eastern Indonesia makes it an interesting area for study. In this research, International Seismological Centre-Engdahl-van der Hilst-Buland catalogue data from 1964 to 2020 were used, which include recorded information on 69.705 earthquake events from 1.185 recording stations and consist of 2.943.974 P phases. Resolution testing was performed using various velocity grids, and optimal results were obtained with a medium resolution of ∼100 km × 100 km × 80 km for the inversion process. The tomographic inversion analysis provided valuable insights into subsurface structures within Earth’s crust and mantle up to a depth of approximately 750 km. The occurrence of deep earthquakes in the study area has provided valuable insights into complex dynamics associated with subduction and plate tectonics. The results of the tomographic inversion analysis reveal that earthquakes are concentrated in areas with high-velocity anomalies, indicating intense tectonic activity near the subduction zone. This study offers the perspective on the structural complexities and earthquake origins in the Sunda–Banda arc transition zone following the 2023 Mw 7.1 Bali Sea earthquake, which occurred on August 29, 2023, at 02:55:32 UTC + 7, approximately 163 km northeast of Lombok, Indonesia. This earthquake was caused by slab pull activity from the Australian Plate and involved a combination of downward and oblique-normal movement. These characteristics indicate the convergence and interaction between tectonic plates in the subduction process occurring in the Bali Sea area. As a result, there have been frequent occurrences of various tectonic and volcanic activities including earthquakes of different magnitudes. These results highlight the significance of the high-velocity anomaly connected to this occurrence, offering valuable insights into seismic behaviour and tectonic phenomena in the region. The findings of this study indicate that the deep earthquakes in the Bali Sea may be induced by faulting due to the transformation of metastable olivine into denser spinel at significant depths, along with shear instability caused by phase transitions within Earth’s mantle layers. This theory proposes that stress-induced changes in phase can initiate shear instabilities and subsequently lead to deep earthquakes.

Keywords: Banda arc; tomography; ISC-EHB data

1 Introduction

The interaction between the Indo-Australian and Eurasian plates has resulted in active faults and geological formations in Bali and its surrounding areas, including a sea trench and an outer arc basin. These features are commonly found in subduction zones where one plate sinks beneath another into the earth’s mantle. Subduction zones are critical on a global scale because they drive plate movement through sinking slabs into the mantle. They also contribute to volcanic eruptions, megathrust earthquakes, and valuable mineral resources [1,2,3]. The subduction process between the Indo-Australian and Eurasian plates primarily influences the tectonic activity in Bali and its neighbouring areas [4]. The study delves into the seismic event in the Lesser Sunda Islands, primarily triggered by the collision of the Australian and Eurasian plates. The tsunami hazard map shows the impact of tsunamis on Bali’s southern coastline, but it fails to consider potential dangers from back arc faults, subsurface landslides, and volcanic activity [5,6,7]. These deep earthquakes result from plastic shear instabilities and shear-induced melting with temperature dependencies. Understanding these geological processes and plate interactions is critical for accurately analysing and predicting seismic activity in the region. Overall, the tectonic activity in Bali and its neighbouring areas, influenced by the subduction process between the Indo-Australian and Eurasian plates, plays a significant role in shaping the seismicity and volcanic activity in the region [8,9]. The movement of the Eurasian, Indo-Australian, and Pacific plates in eastern Indonesia led to the formation of the Banda Seram segment. Additionally, seismic tomography modelling offers valuable insights into the internal structure of Earth beneath the Sunda–Banda arc transition zone [10].

Tectonic plate movement, specifically the subduction process between the Eurasian and Indo-Australian Ocean Plates, triggers seismic events in the region at a rate of 7 cm per year. The primary cause of the south Bali earthquakes is the collision between the Australia and Eurasia plates, which leads to tectonic activity. The Australia Plate is undergoing subduction beneath the Eurasia Plate at a velocity of 6.7 ± 7 millimetres per year in the N11°E ± 4° direction. The Sunda Shelf block is presently undergoing southeastward movement in relation to Eurasia, with an approximate rate of 6 ± 3 mm/year [11,12,13,14,15,16,17].

The Timor–Banda Sea region has a history of significant earthquakes. These events, occurring in 1982, 1996, and 2000, have caused varying degrees of damage and affected multiple regions. On June 22, 1982, there was a magnitude 6.8 earthquake at a depth of 450 km (Figure 1). Another earthquake with a magnitude of 6.6 occurred at a depth of 515 km (Figure 1). This event impacted various regions, including Timor, Bali, Maluku, and the Banda Sea area itself. Additionally, on June 17, 1996, an earthquake measuring approximately M 7.7 (Figure 1) struck the Larantuka and Maumere areas, resulting in damage to the Flores Sea as well as Kupang while causing minor damage elsewhere in Kupang [18]. In recent years, the Banda Sea area has experienced significant seismic activity. On August 28, 2000, a notable earthquake with a magnitude of approximately M 6.5 occurred at a depth of 684 km (Figure 1). The M 7.1 earthquake, located northeast of North Lombok, followed this on August 29. These events have caused damage to various regions, highlighting the need for continued monitoring and study of tectonic activity in this area to ensure community safety and hazard mitigation.

Figure 1

From 1982 to 2023, deep earthquakes with a magnitude ≥6.5 along the subduction zone in eastern Indonesia were distributed [19,20].

Bali, as one of Indonesia’s most commercially valued tourism destinations, has experienced earthquakes at rates of up to 150 each year since 2019. The tectonic activity or volcanic activity of nearby volcanoes can be the source of earthquakes in this region. The seismic activity at Mount Agung in Bali caused significant agitation, monitoring, emergency management, evacuation, and volcanic eruption. Seismic data and historical volcanic event comparisons were major sources of information for early eruption projections. Additional monitoring streams aided in short-term forecasting attempts while the crisis persisted [21,22]. The inversion of long-period P and SH waves, with centroidal depths ranging from 10 to 18 km and uncertainties from 7 to 24 km, identifies deep earthquakes in the Bali Sea. P wave nodal planes dip south at 13° to 35°, indicating crust thrusting beneath the Bali Basin [23]. The recurrence of deadly earthquakes in Bali during the past 5 years serves as a sharp reminder of the island’s seismic vulnerability. Bali residents have faced enormous challenges in dealing with natural disasters, ranging from the catastrophic 6.4 magnitude earthquake in 2018, which claimed more than 20 lives, to the subsequent series of earthquakes in 2019, which caused extensive damage to infrastructure. The frequency and size of these earthquakes have also raised concerns about the region’s preparedness for future seismic activity. Building infrastructure and preparing for future disasters are needed as Bali recovers from recent natural disasters. It is essential to conduct research on the origins of seismic activity in the Bali region, given the increasing frequency of earthquakes documented between 2018 and 2023.

This research used inversion tomography to analyse a data set from 1964 to 2020 – this method is used in seismology to create 3D models of subsurface structures by inverting seismic travel time data. Using inversion with fast marching tomography (FMTOMO), we are able to better constrain the velocity structure of the Earth’s interior, which allows us to gain a clearer understanding of earthquake processes and the dynamics of tectonic plates. This information is crucial for studying seismic hazards and improving our ability to predict and mitigate the impacts of earthquakes. For example, in a study of a seismically active region, researchers may use FMTOMO inversion to create detailed 3D models of the subsurface to identify fault lines and potential earthquake risk zones. This information can then be used by policymakers and urban planners to improve building codes and emergency response plans in order to better protect communities from seismic events. The study specifically focuses on examining velocity structures and their impact on the underlying region. Furthermore, by studying the effects of an M 7.1 earthquake that took place in the Bali Sea in 2023, this research offers valuable insights into understanding subduction zone dynamics and enhancing our ability to mitigate earthquake risks in future.

2 Data and method

2.1 Data

We collected P wave arrival-time data of earthquakes from the International Seismological Centre-EHB Bulletins from 1964 to 2020 (Figure 2). Our dataset includes 2.943.974 arrival times of P waves from 69.705 earthquakes recorded by 1.185 seismic stations in the study region. All of the selected events were located within the study region and recorded at more than ten seismic stations. The residuals for P wave travel times varied widely, with a cut-off residual of ±3 s. We used the AK135 velocity model [24] as the initial velocity model in tomographic inversion.

Figure 2

Distribution map of earthquake epicentre locations collected from the International Seismological Centre-Engdahl-van der Hilst-Buland Bulletins during 1964–2020 [18,19] in eastern Indonesia and earthquake-recording stations.

3 Method

The Fast-Marching Method (FMM) is an efficient method for solving Eikonal equations when Fx is not low. It allows for the accurate and robust modelling of seismic wave propagation. In addition, FMM can be utilized in the inversion of passive seismic methods to determine the hypocentre location [25]. The formulation of the Eikonal equation is as follows:

(1) F ( x ) | ∇ τ x | = 1 ,

where Fx is a function of velocity and x is the arrival time of the wave at point 0. The equation for the first order for 3D fast marching to calculate the arrival time of the wave:

τ = τ i , j , k ,

τ x = min ( τ i − 1 , j , k , τ i + 1 , , j , k ) ,

τ y = min ⁡ τ i , j − 1 , k , τ i , , j + 1 , k ,

(2) τ z = min ⁡ τ i , j , k − 1 , τ i , j , k + 1 ,

(3) max τ − τ x ∆ x 2 + max τ − τ y ∆ y 2 + max τ − τ z ∆ z 2 = 1 F 2 .

The FMM operates by forming a solution in the shortest possible time. The FMTOMO package employed repeated non-linear inversion tomography to account for variations in Vp and Vs [26,27,28,29]. FMTOMO uses the FMM method, a grid-based Eikonal, to advance travel time prediction. The main advantage of this method is that it can produce reliable travel time predictions in areas that have a very heterogeneous velocity structure [30]. In this inversion calculation, the first step is forward modelling to calculate travel time predictions for the dataset used. FMTOMO uses the fast-marching ray tracing method, which is a grid-based numerical method with a finite-difference algorithm. The FMTOMO program [28] employs a subspace inversion method to solve the inversion equation. Subspace inversion is a gradient-based technique and therefore requires Fréchet derivatives. The objective function that invert3d minimizes in order to solve the inverse problem has the form:

(4) S ( m ) = 1 2 [ Ψ ( m ) + ϵ Φ ( m ) + η Ω m ] ,

where ϵ is the damping factor and η is the smoothing factor. In this study, we used ϵ = 10 and η = 5. We applied these values on an ad hoc basis and used the same values for smoothing and damping in the resolution tests. The travel time functions associated with the observation data are as follows [29]:

(5) Ψ ( m ) = ( g ( m ) − d obs ) T C d − 1 ( g ( m ) − d obs ) ,

and object functions associated with the initials of the model

(6) Φ ( m ) = m − m 0 T C m − 1 m − m 0 ,

and the stratigraphic variation function is as follows:

(7) Ω ( m ) = m T D T Dm ,

where gm is the calculation residual, d _obs is the observation residual, and C _d is the covariance data matrix, while m is the model parameter, m 0 is the reference model, C _m is the covariance model matrix and D is the second derivative smoothing operator.

In this study, the process of tomographic inversion began with data preparation, which involved identifying the earthquake source and stations within the Banda arc region. We performed grid parameterization to establish the area for tomographic inversion calculations. For the velocity and propagation grid, we use ∼100 km × 100 km × 80 km. This process also establishes the initial velocity model for the tomography iteration process. We take the initial velocity model from the 1D AK135 velocity model Supplementary S1 [24].

4 Result and discussion

The inversion result has good ray coverage up to 750 km (Figure 3). We constructed a vertical section in the west–east and south–north directions based on the results of previous studies and the resolution test.

Figure 3

Ray path coverage includes horizontal and vertical cross-sections. Grey represents the ray tracing, blue dots represent the earthquake events, and a black reverse triangle represents an earthquake-recording station.

4.1 Resolution test

We conducted the resolution test using the resolution test checkerboard test method. We perturb the initial checkerboard anomalies in pairs and present checkerboard tests of size N = 2. It takes two grid nodes to form a positive or negative anomaly. We conduct the test on three distinct checkerboard sizes: 250 km × 250 km × 100 km for low resolution, 100 km × 100 km × 80 km for medium resolution, and 50 km × 50 km × 25 km for high resolution. The supplementary figure displays the resolution test results (S4 and figure S5). We recovered checkerboard anomalies using the same source-receiver paths that corresponded to the observables and the same input parameters. The best checkerboard recovery occurs in the eastern part of Indonesia, along the Banda arc, the Bali Sea, and the Sunda arc, as we can see in the horizontal cross section. Figure 4 shows the results of horizontal checkerboard tests conducted at various depths. The inversion yields positive results for the entire eastern region of Indonesia at shallow depths, specifically up to 150 km.

Figure 4

Initial velocity model and inversion results for the medium-resolution checkerboard test 100 km × 100 km × 80 km are presented in Figure 4. The horizontal cross-section that results from the inversion includes: (a) the initial velocity model and (b and i) the results of a checkerboard resolution test at depths of 0, 50, 150, 250, 350, 450, 600, and 750 km. We display high velocities in blue and low velocities in red.

However, the research area shows apparent resolution inversion for depths that span 350 km to 600 km. Furthermore, the vertical section from Figure 4 at latitude 6.5° S, Longitude 115° E, 116° E, 117° E, and 118° E” (Figures 5 and 6) in the research area shows the same trend. The resolution test results indicate excellent results up to a depth of 600 km. A gap in station distribution in the study area reduces resolution in this region of the model. We can achieve medium and good resolution down to about 650 km of depth, although the ray path geometry tends to decrease the well-recovered areas as depth increases. Please refer to Figures 5 and 6. We calculated the tomographic inversion using real data on the medium grid.

Figure 5

The upper picture represents the initial velocity model, while the lower figure displays the inversion results derived from the medium-resolution checkerboard test. The vertical cross-section was obtained from the inversion at A-A′ (Latitude 6.5° S) oriented east-west. Blue signifies elevated velocities, whilst red denotes diminished velocities.

Figure 6

(a) Initial model of velocity and inversion results for the resolution test using the medium-resolution checkerboard test method, and (b–e) vertical cross-section resulting from the inversion at B-B′ Longitude 115° E, C-C′ Longitude 116° E, D-D′ Longitude 117° E, and E-E′ Longitude 118° E” with a south–north direction. Blue represents the high velocities, while red represents low velocities.

5 Result and discussion

In Figure 7, Section A-A′, a high-velocity anomaly is observed in the eastern part of the region. This anomaly extends for approximately 200 km and corresponds to the subduction zone beneath Java Island in Indonesia. Subduction zones, where one tectonic plate forces beneath another, give rise to various geological phenomena such as volcanic eruptions, earthquakes, and seismic events [31,32]. Low-velocity anomalies between 200 and 400 km indicate a subducted oceanic lithosphere beneath Java Island. These findings suggest ongoing tectonic activity associated with subduction processes [9,33,34]. The subduction of the Indo-Australian Plate beneath the Eurasian Plate in the Java Trench directly influences geological activities such as volcanic eruptions, earthquakes, and other seismic events in this region. Cross-section A-A′ reveals several deep earthquakes occurring within regions characterized by high seismic velocities ranging from 450 to 670 km. These velocity anomalies in the lower mantle highlight the complex processes that occur within subducting slabs. Studying seismic velocity anomalies in subduction zones provides a deeper understanding of subduction mechanisms and plate tectonics. Furthermore, some previous studies have suggested that various factors, such as plastic instabilities, shear-induced melting, recrystallization, or polymorphic phase transformation, could potentially play a role in triggering these deep-seated earthquakes [35,36]. The study of seismic velocity anomalies in subduction zones provides valuable insights into plate tectonics and subduction dynamics. Either plate subduction or the upward movement of mantle material could cause these deep earthquakes. Since these deep earthquakes happen in areas with high seismic velocities, it is possible that fluids from subducted oceanic crust that are dry could be the cause of lower seismic velocities in some places [37,38].

Figure 7

Horizontal and vertical cross-sections of the tomographic inversion result show anomalies in velocity. Blue signifies the high velocity, while red correlates with low velocity. The red star represents the epicentre of a deep earthquake, and the dashed line marks the mantle transition. Hypocentre earthquakes are represented by white dots.

In section B-B′ of Figure 7, it is shown that there are steeply dipping high-velocity anomalies extending to the northern part of the Bali Sea up to a depth of 400 km. There is a possibility that the occurrence of high-velocity anomalies is connected to the mass density that is associated with the subduction of the oceanic plate beneath the island of Bali, which implies the presence of a subducted slab in this location. In the Bali Sea region, where the Indo-Australian plate is subducting beneath the Eurasian plate, we suggest that high-velocity anomalies indicate the presence of a subducted slab. These anomalies arise because subducted slabs consist of cold, dense oceanic lithosphere that has descended into the Earth’s mantle. Due to its lower temperature and higher density compared to the surrounding mantle material, the subducted slab allows seismic waves to travel faster through it, resulting in the detection of these high-velocity anomalies in seismic tomography. The occurrence of high-velocity anomalies might be related to processes like subduction of the Indo-Australian plate or the existence of a deep-seated structure like a mantle wedge [9,34,39]. The presence of a deflected high-velocity anomaly from 400 to 600 km in the deeper part of the B-B′ cross-section suggests the variations in strength parameters at the subduction interface and mantle wedge, as well as inter-plate friction coefficients, likely contribute to these behaviours. Different mechanisms operate at varying depths in subduction zones, with brittle deformation dominating in shallower areas and ductile behaviour prevailing in deeper sections. The observed variation can be attributed to factors such as the subduction angle, properties of materials being subducted, and interactions between lithospheric plates. The Bali Sea subduction zone experiences both thrust-faulting earthquakes and along-arc compression, indicating a combination of brittle and ductile deformation. Overall, the Sunda–Banda arc transition is an area characterized by intense seismic activity influenced by various processes such as subduction, collision, back-arc thrust faults, and the presence of a slab window or missing subduction material [18]. The behaviours in this area are influenced by variations in strength parameters at the subduction interface and mantle wedge, as well as inter-plate friction coefficients. Ongoing research and monitoring are necessary to improve our understanding of subduction zone dynamics [40]. The Bali Sea subduction zone experiences both thrust-faulting earthquakes and along-arc compression, indicating a combination of brittle and ductile deformation.

The earthquake on August 29, 2023, in the eastern area with a C-C′ cross section (Figure 7) occurred in a region with high velocities. Deep earthquakes in this region may be a result of the interaction between the subducting lithosphere and the surrounding mantle. Studies [37,41,42,43,44] suggest that transformational faulting, resulting from the phase transformation of metastable olivine to denser spinel at great depths, triggers deep earthquakes. One possible explanation for the occurrence of deep earthquakes in regions with high-velocity anomalies is the interaction between the subducting lithosphere and the surrounding mantle [45,46]. Deep earthquakes present a challenge in terms of understanding their mechanisms and how they relate to mantle dynamics. The feasibility of transformational faulting being responsible for deep earthquakes depends on the presence of a sufficient amount of metastable phase within them [47,48,49]. Factors such as the thermal structure of slabs and stress conditions at the upper-lower mantle boundary influence the viability of these different mechanisms [50,51].

The Sunda–Banda transition zone shows intriguing results in both D-D′ and E-E′ (Figure 7). These regions, located within the transition zone, have been a subject of interest for geologists and researchers due to the presence of an old subduction beneath Borneo Island in Indonesia. The relationship between this old subduction zone and seismic velocity is currently under active investigation. External stresses from sources such as the Australia–Indonesia collision zone, deformation around Sulawesi, or collisional events in the Philippines are believed to influence the reactivation of the old subduction beneath Borneo Island [52,53]. A comprehensive understanding of the geological processes at play requires further investigation into the relationship between old subduction beneath Borneo Island in Indonesia, seismic velocity variations, and tectonic events. This includes examining the presence of a “slab window” or “window of missing subduction material” in the slab beneath the Sunda–Banda transition subduction zone [9,34,39]. Figure 7 displays the gap at depths below 350 km in the Sunda–Banda subduction zone on the D-D′ and E-E′ cross-sections. A transition in stress and heterogeneity within the slab is believed to cause this gap in the subducting slab. It is a significant geological feature with implications for tectonic processes and dynamics in this subduction zone [9,34,39,43,54]. The subducted slab structure in the lower mantle is related to the Tertiary evolution of south-eastern Asia and the Indian Ocean region [9,56]. Further studies are required to investigate the correlation between old subduction beneath Bali Island in Indonesia and seismic velocity variations, as well as their implications for tectonic activity.

According to Zhu et al. [56], the low-velocity anomalies in the oceanic plate may offer some hints regarding the significant intraplate seismicity, while the high-velocity anomalies from tomographic pictures are typically understood as subducting lithosphere or mantle plume in the deep, respectively. Deep earthquakes in the A-A′ to E-E′ cross-section may be caused by transformational faulting, an occurrence that happens when metastable olivine changes phases to become denser spinel. This phenomenon is caused by variances in velocity that are considerably higher than the average, as well as the interaction between the falling lithosphere and the surrounding mantle. Understanding the mechanisms and relationship between deep earthquakes and mantle dynamics is a challenging endeavour. The presence of a sufficient metastable phase is necessary for transformational faulting to be the cause; these mechanisms are influenced by the slab’s thermal structure and the stress conditions at the upper–lower mantle boundary. Based on the result of tomographic inversion, the occurrences of deep earthquakes are associated with regions of high P-wave velocity anomalies, which are linked to subduction zone. Therefore, earthquakes are likely to occur along these high-velocity anomalies. However, the precise location of potential earthquakes cannot yet be determined within the context of earthquake prediction. This study concludes that the earthquake on August 29, 2023, with magnitude greater than M7 and occurring at a depth of 512 km, is linked to a region of high-velocity anomaly. While this anomaly may result from various factors, geological history analysis suggests a connection to ancient subduction processes. Tomographic inversion results support the hypothesis that the earthquake is most plausibly associated with the presence of metastable olivine in the upper mantle transition zone.

Further research is needed to understand the relationship between old subduction, seismic velocity variations, and tectonic activity in the Sunda–Banda transition zone. Understanding factors such as far-field stresses, deformation around Sulawesi, and collisional events in the Philippines could help us understand the Earth’s crust. Tomography seismic data collected after a significant earthquake can provide a better understanding of the Earth’s lithosphere’s structure and behaviour in this complex area. This information can enhance preparedness efforts and response strategies for future seismic events. The insights gained from tomography seismic technology could have broader implications for geodynamics and plate tectonics, shedding light on the dynamic processes shaping the Earth’s surface and deep interior. The continuous study and use of tomography seismic data hold great promise for advancing our knowledge of tectonic processes in geologically complex areas worldwide.

6 Conclusion

Seismic velocity anomalies in subduction zones may provide insight into the mechanics of subduction and plate tectonics. The high-velocity anomalies observed to the western part of study region, extending over a length of 200 km, exhibit a strong correlation with the subduction zone located beneath Java Island, Indonesia. Low-velocity anomalies suggest the presence of a subducted oceanic lithosphere beneath Java Island. Examining these irregularities provides a valuable understanding of the movements of tectonic plates and the process of subduction. It indicates that plastic instabilities, shear-induced melting, recrystallization, or polymorphic phase transformation may be possible triggers for these earthquakes that occur deep within the Earth. The subduction zone in the Bali Sea undergoes both thrust-faulting earthquakes and along-arc compression, which suggests a mixture of brittle and ductile deformation. This study concludes that the August 29, 2023, earthquake, with a magnitude greater than M7 and 512 km depth, is linked to a high-velocity anomaly, possibly due to ancient subduction processes. Tomographic inversion results suggest that the earthquake is most likely associated with metastable olivine in the upper mantle transition zone.

Acknowledgement

We thank Ministry of Education, Culture, Research and Technology for Scholarship.

Author contributions: Mia Uswatun Hasanah: Writing – original draft, Visualization, Resources, Methodology, Investigation, Formal analysis, Conceptualization. Pepen Supendi: Writing – review & editing, Supervision, Conceptualization. Andri Dian Nugraha : Writing – review & editing, Supervision, Formal analysis. Sri Widiyantoro: Writing – review & editing, Supervision, Formal analysis. Firman Syaifuddin: Visualization, Data curation.
Conflict of interest: Authors state no conflict of interest.
Data availability statement: The data is open source at https://www.isc.ac.uk/isc-ehb/search/.

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Received: 2024-01-10

Revised: 2024-09-20

Accepted: 2024-09-22

Published Online: 2024-11-09

This work is licensed under the Creative Commons Attribution 4.0 International License.

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https://doi.org/10.1515/geo-2022-0710

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Banda arc; tomography; ISC-EHB data

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The new insight of tectonic setting in Sunda–Banda transition zone using tomography seismic. Case study: 7.1 M deep earthquake 29 August 2023

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Abstract

1 Introduction

2 Data and method

2.1 Data

3 Method

4 Result and discussion

4.1 Resolution test

5 Result and discussion

6 Conclusion

Acknowledgement

References

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