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Introduction: On November 21, 2022, a magnitude Mw 5.6 earthquake struck Cianjur Regency in the West Java Province of Indonesia. It was followed by at least 512 aftershocks that persisted from November to June 2023. This seismic event occurred in an area previously unrecognized as an active fault zone. The consequences of this earthquake in Cianjur were severe, leading to both loss of life and extensive structural damage. The substantial damage to buildings was likely a result of abrupt alterations in the local topography due to surface deformation effects. Objectives: This research endeavor aims to spatially determine the patterns of ground surface deformation and its relationship with local geomorphological setting due to earthquakes in Cianjur in 2022. Methods: In this study we conduct seismological analysis of 45 seismic stations, statistical analysis of mainshock and aftershocks data, RADAR Sentinel-1 imagery and employed the DInSAR methodology. Field survey was also conducted to determine the geomorphological characteristics in the study area. Results: The outcomes disclosed that the deformation encompassed both subsidence and uplift. The results signify that there was subsidence deformation in the vicinity of Cianjur and its environs during the primary earthquake on November 21, 2022, with an average deformation value of approximately -5 cm. In contrast, the measured deformation during the aftershocks exhibited uplift deformation, with an average value of 10 cm. The examination of deformation patterns amid the 2022 Cianjur earthquake sequence detects elevated deformation values in the vicinity of Cugenang district, with an orientation running from northwest to southeast. The geomorphological investigation conducted indicates that the region of Cianjur encompasses a variety of landforms, such as volcanic, structural, fluvial, and denudational. These landforms exhibit distinct responses to seismic activities. Co-seismic hazards, such as landslides frequently occur as a consequence of seismic events in mountainous terrain. Main Conclusions: Spatio-temporal variation of ground deformation could arise from various causes, such as the number and distribution of aftershocks, stress redistribution, fault interactions, secondary effects, and local geological settings. The mainshocks release accumulated stress along a fault, resulting in particular types of deformation, whereas aftershocks may redistribute stress exhibiting on adjacent faults. Secondary effects triggered by aftershocks, coupled with local geological and geomorphological conditions, further contribute to the diverse patterns of ground deformation observed during seismic events. The results of the study revealed that ground deformation had the greatest impact on fluvial, volcanic, and denudational processes, resulting in notable subsidence and uplift in specific regions. The occurrence and magnitude of co-seismic landslides were triggered by both mainshock and aftershock events, which occurred on weathered geological materials. These effects were further amplified by the simultaneous presence of the rainy season. Implications: The knowledge gained from this research can be applied to evaluate the impacts of earthquakes and to proactively reduce future risks. [ABSTRACT FROM AUTHOR]

Mount Semeru, one of the world's most active volcanoes, experiences frequent eruptions and at least one significant eruption annually. Traditional monitoring methods, constrained by the existing geodetic infrastructure, have been augmented by Interferometry Synthetic Aperture Radar (InSAR) technology. Previous InSAR applications in Indonesia have primarily relied on Line-of-Sight (LOS) displacement measurements, utilizing a single orbital geometry. This study breaks new applications by leveraging two orbital geometries of the Sentinel-1 satellite, advancing beyond conventional one-dimensional observations to generate comprehensive multidimensional displacement time series. This approach enables the precise capture of vertical, east-west, and north-south components of surface motion at Semeru volcano. Our findings underscore the critical role of multitrack InSAR data in providing a nuanced understanding of volcanic deformation. By encompassing all three displacement components, our methodology delivers a more detailed and accurate depiction of the volcano's dynamics. Although the 2.5D displacement model proves adequate in certain scenarios, the full three-dimensional analysis reveals its superiority in monitoring slow surface deformation. This study not only demonstrates the enhanced capabilities of InSAR in volcanic monitoring but also sets a precedent for its application in other high-risk volcanic and tectonic regions. Furthermore, our research emphasizes the value of integrating InSAR data with other monitoring techniques, like the Global Navigation Satellite System (GNSS), for cross-validation and accuracy enhancement. The synergy of these technologies offers a powerful tool for geoscientists, potentially enhancing our understanding of surface motion and contributing to more effective risk management in geologically active areas. [ABSTRACT FROM AUTHOR]

Interferometric Synthetic Aperture Radar (InSAR) is a radar technique to generate map of surface deformation using phase differences acquired at different times. The InSAR technique measures these phase differences in its line of sight (LOS). Regarding LOS projection to a ground coordinate system, the combination of SAR data from ascending and descending can estimate at least two dimensional fields which are vertical and east-west components and three dimensional fields with either an additional motion model or vector displacements from along-track direction. The purpose of this work is to generate 2D and 3D vector displacements from two different InSAR tracks (e.g. ascending and descending) with a calculation programme both for the mean velocity and time series data named as PS DISP. 2D mode is calculated in which the north-south component is neglected due to insensitive along the flight direction, thus, assuming to be zero (0). On the other hand, 3D mode is calculated with an assumption that the northsouth component moves along the elevation downward. The experimental results were conducted for the Puncak Pass and Puncak Highway landslides and the Lombok earthquake in Indonesia. For the landslide study, the computation generated the movement towards the slope surface in the 3D Cartesian coordinate (dU,dE, and dN (psuedo)) and found both the crown body and cumulative zone of the landslide. For the earthquake study, PS DISP decomposed 2D vectors (dU and dE). The area of earthquake rupture was lifted by 42 cm and other northern Lombok areas by 10 - 25 cm. Regarding the west-eastern motion, it shows that the west of northern Lombok was displaced ±5 cm toward the west direction, while the other side to the east direction. [ABSTRACT FROM AUTHOR]

Tropical peatland in Southeast Asia has undergone rapid degradation and shows large subsidence due to oxidation and peat shrinkage. The measurement of those deformations is thus valuable for evaluating the peat condition and assessing peat restoration. The time series interferometric synthetic aperture radar (TInSAR), especially with the small baseline subsets (SBAS) method, is capable of measuring long-term deformation. However, the dynamic surface scatterers often change in tropical peatland, which degrades the coherent scatterer (CS) distribution density. This article presents a simple and efficient TInSAR approach that enhances the CS density under such dynamic surface scatter variation based on the SBAS method. In the presented approach, a long-time series of single-look complex images is separated into subsets, and deformation estimation is performed for each subset. The effectiveness of this simple solution was investigated by InSAR simulation and validated using SAR observation data. We applied the subset SBAS approach to the three-year Sentinel-1A C-band SAR dataset acquired over tropical peatland in Indonesia. The analyses showed an improved number of CSs for the introduced subset approach. We further introduce the color representation of CS temporal behavior per subset for visual interpretation of scatterer change. [ABSTRACT FROM AUTHOR]

Landslides are a common type of disaster in Indonesia, especially in steepslope areas. The landslide process can be well understood by measuring the surface deformation. Currently, there are no practical solutions for measuring surface deformation at landslide locations other than field surveys in the Pacitan Regency. We apply LiCSBAS, to identify surface deformation in several landslide locations in a specific non-urban area with mixed topographical features. LiCSBAS is a module that utilizes data from the project of looking inside the continent from space (LiCS), using the new small baseline area subset (NSBAS) method. This study utilizes the leaf area index (LAI) to validate the ability of LiCSBAS to detect surface deformation values at landslide locations. The study succeeded in identifying surface deformations at 100 landslide locations, with deformation values ranging from 15.1 to 10.9 millimeters per year. Most of the landslide locations are closely related to volcanic rocks and volcanic sediments on slopes of 30-35°. The NSBAS method in the LiCSBAS module can reduce gaps error in the sentinel-1 image network. However, the utilization of the C-band at a pixel size of 100 meters made surface deformation only well detectable in a large open landslide area. [ABSTRACT FROM AUTHOR]

Landslide is a natural phenomenon that frequently occurs on the Java Island of Indonesia, causing significant damage and casualties. Due to advances in remote sensing technology, radar imaging can detect and evaluate ground surface deformation. This study examines the ground surface deformation and displacement in each landslide location in terms of spatial and temporal and identifies the different types and characteristics of landslides in the Sukabumi area of West Java, Indonesia. The Small Baseline Subset Interferometric Synthetic Aperture Radar (SBAS-InSAR) methodology was used in this study, and the DinSAR method was applied. We combined the LiCSAR data product with the Python coding-based LiCSBAS processing package to derive a surface displacement value at each landslide location. The results show that the DinSAR approach can detect surface deformation by integrating the LiCSAR product with the Python coding-based LiCSBAS processing software. According to quantitative data, the research area experienced surface deformation with a surface displacement velocity of -36,297 mm/year to 58,837 mm/year. The ground surface displacement at each landslide location ranged from -9.79 mm/year to +33.69 mm/year, with most of the landslides occurring on moderate to steep slopes (160-350). These results are suitable to use for support regional development planning in reducing losses and casualties. [ABSTRACT FROM AUTHOR]

This study proposes the entire detection of the surface deformation of a volcanic area using interferometric synthetic aperture radar (InSAR) with geostatistics to specify the locations and shapes of the sources causing the deformation. We selected the Tangkuban Parahu area, West Java, Indonesia, as our study site and used a Sentinel-1 dataset. In this study, we combine persistent scatterer and small baseline subset InSAR with a geostatistical technique, i.e., turning bands simulation. This combination can compensate for undetected displacement pixels and decompose the line-of-sight displacement into vertical and horizontal east–west displacements using both the ascending and descending mode results and the least-squares method. This two-dimensional geostatistics and multitemporal InSAR approach is referred to as 2D GMT-InSAR. A detailed displacement pattern is revealed by 2D GMT-InSAR for undetected pixels in low-coherence areas. Then, the vertical displacement pattern in the study period from 2014 to 2019, mainly uplift with local subsidence, is reproduced via the joint use of the Mogi and Okada models for circular and rectangular parallelepiped sources of the deformation, respectively. Via a Bayesian inversion, one circular source, equivalent to a magma reservoir, and one dyke source are identified. The displacement pattern is likely caused by pressure increases in the magma reservoir, associated with the volcanic activation, and in the dyke, associated with the gas and fluid flows from the reservoir, which induced a phreatic explosion in July 2019. A connection of the dyke with the old Sunda volcanic system is found; this new finding is a result of the caldera collapse during the Sunda volcanic eruption. • Up–down and east–west displacements were revealed via turning bands simulations • Volcanic uplift before a 2019 eruption was detected by InSAR with geostatistics • Inversion of interpolated InSAR data was effective to estimate magma reservoir system • Two shallow magma reservoirs were located at depths of ∼1100 m and 3700 m • These reservoirs were likely formed by collapse and evolution of a nearby volcano [ABSTRACT FROM AUTHOR]

We simulate surface displacements calculated on homogeneous and layered half-space and spherical models as applied to the coseismic and postseismic (afterslip and viscoelastic relaxation) of the 2006 Java tsunami earthquake. Our analysis of coseismic and afterslip deformation suggests that the homogeneous half-space model generates a much broader displacement effect than the layered half-space and spherical models. Also, though the result for surface displacements is similar for the layered half-space and spherical models, noticeable displacements still occurred on top of the coseismic fault patches. Our displacement result in afterslip modeling suggests that significant displacements occurred on top of the main afterslip fault patches, differing from the viscoelastic relaxation model, which has displacements in the front region of coseismic fault patches. We propose this characteristic as one of the important features differentiating a postseismic deformation signal from afterslip and viscoelastic relaxation detected by geodetic data. [ABSTRACT FROM AUTHOR]

Abstract: The paper illustrates the application of high-spatial resolution satellite images in interpreting volcanic structures and eruption impacts in the Tengger–Semeru massif in east Java, Indonesia. We use high-spatial resolution images (IKONOS and SPOT 5) and aerial photos in order to analyze the structures of Semeru volcano and map the deposits. Geological and tectonic mapping is based on two DEMs and on the interpretation of aerial photos and four SPOT and IKONOS optical satellite images acquired between 1996 and 2002. We also compared two thermal Surface Kinetic Temperature ASTER images before and after the 2002–2003 eruption in order to delineate and evaluate the impacts of the pyroclastic density currents. Semeru''s principal structural features are probably due to the tectonic setting of the volcano. A structural map of the Tengger–Semeru massif shows four groups of faults orientated N40, N160, N75, and N105 to N140. Conspicuous structures, such as the SE-trending horseshoe-shaped scar on Semeru''s summit cone, coincide with the N160-trending faults. The direction of minor scars on the east flank parallels the first and second groups of faults. The Semeru composite cone hosts the currently active Jonggring-Seloko vent. This is located on, and buttressed against, the Mahameru edifice at the head of a large scar that may reflect a failure plane at shallow depth. Dipping 35° towards the SE, this failure plane may correspond to a weak basal layer of weathered volcaniclastic rocks of Tertiary age. We suggest that the deformation pattern of Semeru and its large scar may be induced by flank spreading over the weak basal layer of the volcano. It is therefore necessary to consider the potential for flank and summit collapse in the future. The last major eruption took place in December 2002–January 2003, and involved emplacement of block-and-ash flows. We have used the 2003 ASTER Surface Kinetic Temperature image to map the 2002–2003 pyroclastic density current deposits. We have also compared two 10m-pixel images acquired before and after the event to describe the extent and impact of an estimated volume of 5.45×106 m3 of block-and-ash flow deposits. An ash-rich pyroclastic surge escaped from one of the valley-confined block-and ash flows at 5 to 8km distance from the crater and swept across the forest and tilled land on the SW side of the Bang River Valley. Downvalley, the temperature of the pyroclastic surge decreased and a mud-rich deposit coated the banks of the Bang River Valley. Thus, hazard mitigation at Semeru should combine: (1) continuous monitoring of the eruptive activity through an early-warning system, and (2) continuous remote sensing of the morphological changes in the drainage system due to the impact of frequent pyroclastic density currents and lahars. [Copyright &y& Elsevier]

Abstract: Newly pre-stack depth-migrated seismic images resolve the structural details of the western Java forearc and plate interface. The structural segmentation of the forearc into discrete mechanical domains correlates with distinct deformation styles. Approximately 2/3 of the trench sediment fill is detached and incorporated into frontal prism imbricates, while the floor sequence is underthrust beneath the décollement. Western Java, however, differs markedly from margins such as Nankai or Barbados, where a uniform, continuous décollement reflector has been imaged. In our study area, the plate interface reveals a spatially irregular, nonlinear pattern characterized by the morphological relief of subducted seamounts and thicker than average patches of underthrust sediment. The underthrust sediment is associated with a low velocity zone as determined from wide-angle data. Active underplating is not resolved, but likely contributes to the uplift of the large bivergent wedge that constitutes the forearc high. Our profile is located 100km west of the 2006 Java tsunami earthquake. The heterogeneous décollement zone regulates the friction behavior of the shallow subduction environment where the earthquake occurred. The alternating pattern of enhanced frictional contact zones associated with oceanic basement relief and weak material patches of underthrust sediment influences seismic coupling and possibly contributed to the heterogeneous slip distribution. Our seismic images resolve a steeply dipping splay fault, which originates at the décollement and terminates at the sea floor and which potentially contributes to tsunami generation during co-seismic activity. [Copyright &y& Elsevier]