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Abstract 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.

In this article, desertification and dune progression over vegetation was quantified using remote sensing data. However, vegetation buried under sand blowout could not be counted using this method. Therefore, to estimate the extent of buried vegetation, a GPR campaign was conducted over the coastal sand-dune of Tottori Prefecture (Japan) in combination with a high-resolution topographic UAV-based survey of the topography. The results show that buried vegetation exists underneath sand-blowout, especially near the dune ridges, and can extend from 20 to 30 meters further than the estimate based on airborne remote sensing. Furthermore, the presence of palaeo-vegetation in palaeodune layers also provides the information on the long-term evolution of sand dunes, which can be used to reconstruct Quaternary coastal environments.

Lahar hujan merupakan suatu fenomena kebencanaan yang mengancam daerah sekitar gunungapi, namun juga memiliki dampak positif berupa potensi pertambangan yang besar. Berdasarkan hal tersebut perlu adanya pengelolaan dan perencanaan, didukung oleh informasi spasial yang memadai salah satunya adalah ukuran butir. Berkembangnya produk penginderaan jauh dan sistem informasi geografi dapat digunakan sebagai penyedia data spasial ukuran butir. Fokus penelitian ini adalah pemanfaatan Citra Sentinel-2 melalui indeks ukuran butir untuk mengestimasi ukuran butir menggunakan pendekatan empiris. Tahap penelitian terdiri dari pra-pemrosesan citra, pengambilan ukuran butir lapangan, analisis laboratorium, pemodelan empiris, dan identifikasi sebaran ukuran butir. Hasil penelitian menunjukkan indeks ukuran butir berkorelasi terhadap ukuran butir dan dapat digunakan sebagai variabel pemodelan. Ukuran butir pada lokasi penelitian berkisar antara -0.050 Φ sampai 11.828 Φ. Nilai validitas tergolong baik dikarenakan model memiliki nilai kesalahan estimasi yang setara dengan satu kelas ukuran butir. Distribusi ukuran butir menunjukkan semakin jauh transportasi material diiringi dengan semakin kecilnya ukuran butir.

This study has two aims: to determine the spatial distribution of multi-hazard levels and to discover the interactions, interdependencies, and effects that cascade among hazards in Gunungkidul Regency, Special Region of Yogyakarta. A multi-hazard map was created with a scale of 1:250,000 and modelled using SMCE (Spatial Multi-Criteria Evaluation). The conditioning factors used included slope, rainfall, historical data, river distance, geomorphology, land cover, lithology, and fault distance. The selected conditioning factors for each hazard were then weighted using weighted overlay analysis. The results showed that the area of Gunungkidul can be included in the high-risk category for floods, since the probability of flooding is 56.72%, the probability of landslides is 9.14%, that of drought is 48.86%, and that of seismic disturbance is 20.83%. (Multi-hazard maps are created by overlaying flood, landslide, seismic, and drought hazard maps.) After these risk factors were calculated, the regions on the multi-hazard map were re-categorized into five hazard classes. All areas in Gunungkidul Regency have multiple hazards, with risk factors of different magnitudes. The interaction between hazards can generate new hazards that are called cascading hazards. The cascading hazards in the study area are most likely to occur in the north of Gunungkidul Regency with its very high seismic and landslide hazard risk factors, due to the geological and geomorphological conditions of the Baturagung Structural Hills.

Landslide dams are less frequent than other landslides, and their very existence is often very-much short-lived, because the temporary dam tends to collapse rapidly. Because of the resulting lack of evidences, there has been less research done on this topic, although the potential catastrophe they can be at the origin of needs assessment. For this purpose, the present contribution aims at differentiating landslides that trigger dams against those that do not inside a group of valleys of the Kii peninsula in Japan, where landslides occurred after the typhoon Talas in 2011. Using topographic map before the event and LiDAR data in its aftermath, the authors have calculated the factor of safety (FS) of different landslides in the same valleys, comparing the data of landslides that created dams against those that did not. The results show that landslides that triggered dams seemed to have a higher FS than those that did not. The authors suggest that it is because larger landslides are needed and thus appear more stable, but also because at the location where the slopes are stable, the riverbed can incise further instead of growing horizontally, and thus the sediments damming the channel have more chances to block it (as it is narrow) and stop the river from flowing.

The research set out to analyze coastal typology characteristics and ecotourism development through geomorphosite assessments and suggest fitting management strategies in East Lombok, Indonesia. In this research, the connection between ecotourism potentials and coastal typologies was investigated. The methods of this research were conducted using a combination of GIS-based analysis and field surveys. Geomorphosites were assessed from several facets or attributes: scientific and intrinsic, educational, economic, conservation, and added values. The analysis results showed that two coastal geomorphosites could be developed into ecotourism spots, as supported by East Lombok’s regional planning to promote ecotourism in its tourism branding. In addition, the sites are suggested to develop local products as a part of their attractiveness. Another finding is that the coastal typology has a strong connection to the scoring result, especially the scientific-intrinsic and conservation values.

Yogyakarta is one of the large cities in Central Java, located on Java Island, Indonesia. The city, and the Pleret sub-district, where the study has taken place, is prone to earthquake hazards, because it is close to several seismically active zones, such as the Sunda Megathrust and the active fault known as the Opak Fault. Since a devastating earthquake of 2006, the population of the Pleret sub-district has increased significantly. Thus, the housing demand has increased, and so is the pace of low-cost housing that does not meet earthquake-safety requirements, and furthermore are often located on unstable slopes. The local alluvial material covering a jigsaw of unstable blocks and complex slope is conditions that can amplify the negative impacts of earthquakes. Within this context, this study is aiming to assess the multi-hazards and risks of earthquakes and related secondary hazards such as ground liquefaction, and coseismic landslides. To achieve this, we used geographic information systems and remote sensing methods supplemented with outcrop study and existing seismic data to derive shear-strain parameters. The results have revealed the presence of numerous uncharted active faults with movements visible from imagery and outcrops. show that the middle part of the study area has a complex geological structure, indicated by many unchartered faults in the outcrops. Using this newly mapped blocks combined with shear strain data, we reassessed the collapse probability of buildings that reach level >0.75 near the Opak River, in central Pleret sub-district. Classifying the buildings and from population distribution, we could determine that the highest risk was during nighttime as the buildings susceptible to fall are predominantly housing buildings. The secondary hazards follow a slightly different distribution with a concentration of risks in the West.

Kotawaringin Barat is a high-risk area for forest and land fires; a total of 564.13 km2 of forest land was burned from 2015 to 2022, the majority of which spread to peatlands. The goal of this contribution is to use the information value method (IVM) to construct forest and land fire spatial susceptibility maps for the Kotawaringin Barat regency. MODIS hotspots from 2016 to 2020 were used as the dependent variable, with six independent variables included in the modeling. According to the data, there were 925 hotspots detected in Kotawaringin Barat between 2016 and 2020. The areas closest to rivers and roads are more susceptible to forest and land fires, while the areas closest to settlements are safer. Flat slopes have an IVM of 0.697, while peatlands have an IVM of 0.667, making them the most susceptible to forest and land fires. Furthermore, the most susceptive land covers are swamps (IVM = 1.071) and shrublands (IVM = 0.024). According to the IVM model of susceptibility mapping, Kotawaringin Barat is categorized as very high (18.32%) and high (27.97%) risk. About 33.57% of the study area is classified as moderately susceptible, while the remaining 20.14% is classified as low risk. The accuracy of the IVM for forest and land fires is 66.87% (AUC), indicating that the model can be used for susceptibility assessments particularly for very high to high susceptibility areas.

This is the first study discussing the dynamics of two caldera-forming eruptions in the Banda volcanic complex (BVC) in the marine conservation zone of Banda, Maluku, Indonesia. The first and second caldera episodes are, hereafter, termed as Banda Besar and Naira, respectively. The formation of Banda Besar caldera (ca. 8 × 7 km) ejected homogeneous rhyolitic magmas (bulk-rock, 73.1–73.8 wt.% SiO2) in the following three stages: (1) sub-Plinian (BB-5a), (2) intra-sub-Plinian flow (BB-5b), and (3) caldera collapse (BB-5c and BB-5d). The BB-5a stage produced a reversely graded white pumice fall layer with moderate lithics (2–11%), which originated from a sub-Plinian eruption with an estimated plume height of 22–23 km. Subsequently, intensive erosion of wall rock (13–25%) causes conduit enlargement, leading to the partial collapse of the eruption columns, forming intra-sub-Plinian flow deposits (BB-5b). It is likely that conduit size surpassed the minimum threshold value for a buoyant plume during the final phase of the second stage, causing the complete formation of a pumice-rich pyroclastic density current (PDC) during the early-third stage (BB-5c). Finally, the evacuation of voluminous magma from the reservoir yields the first caldera collapse during the late-third stage, producing a lithic-dominated PDC with minor pumices (BB-5d). The formation of the Naira caldera (ca. 3 × 3 km) ejected homogeneous dacitic magmas (bulk-rock, 66.2–67.2 wt.% SiO2) in the following three stages: (1) early sub-Plinian (N-2a and 2b), (2) late sub-Plinian (N-2c, 2d, 2e), and (3) caldera collapse (N-2f). This research distinguishes the sub-Plinian into two stages on the basis of different vent locations (assumed from the isopach map). In particular, this research suggests that the early sub-Plinian stage (N-2a and 2b) erupted from the northern vent, producing 14 and 8 km eruption plume heights, respectively. Additionally, the late sub-Plinian stage (N-2c, 2d, 2e) was generated from a newly-formed conduit located in the relatively southern position, producing 12–17, 9, and 6 km eruption plume heights, respectively. Conduit enlargement is expected to occur during at both sub-Plinian stages, as lithic portions are considerably high (10–72%) and ultimately generate PDCs during the third stage (caldera collapse; N-2f). Because most of the erupted materials (for both caldera-forming eruptions) are emplaced in the ocean, estimating the erupted volume becomes difficult. However, with the assumption that the caldera dimension represents the erupted volume of magma (Vmagma), and that the total erupted volume (Vtotal) is a summation of Vmagma and the now-vanished pre-caldera island (Vvanished, represented by average lithic fractions), the first and second caldera might produce (at least) 35.2 and 2.4 km3 of erupted materials, scaling them as VEI (volcano explosivity index) 6 and 5, respectively. That VEI is more than enough to initiate a secondary hazard in the form of tsunamis triggered by volcanic activities.

Spatial approaches, based on the deformation measurement of volcanic domes and crater rims, is key in evaluating the activity of a volcano, such as Merapi Volcano, where associated disaster risk regularly takes lives. Within this framework, this study aims to detect localized topographic change in the summit area that has occurred concomitantly with the dome growth and explosion reported. The methodology was focused on two sets of data, one LiDAR-based dataset from 2012 and one UAV dataset from 2014. The results show that during the period 2012–2014, the crater walls were 100–120 m above the crater floor at its maximum (from the north to the east–southeast sector), while the west and north sectors present a topographic range of 40–80 m. During the period 2012–2014, the evolution of the crater rim around the dome was generally stable (no large collapse). The opening of a new vent on the surface of the dome has displaced an equivalent volume of 2.04 × 104 m3, corresponding to a maximum −9 m (+/−0.9 m) vertically. The exploded material has partly fallen within the crater, increasing the accumulated loose material while leaving “hollows” where the vents are located, although the potential presence of debris inside these vents made it difficult to determine the exact size of these openings. Despite a measure of the error from the two DEMs, adding a previously published dataset shows further discrepancies, suggesting that there is also a technical need to develop point-cloud technologies for active volcanic craters.

Lombok Island in Indonesia was hit by four major earthquakes (6.4 Mw to 7 Mw) and by at least 818 earthquakes between 29 July and 31 August 2018. The aims of this study are to measure ground deformation due to the 2018 Lombok earthquake series and to map its spatio-temporal distribution. The application of DinSAR was performed to produce an interferogram and deformation map. Time series Sentinel-1 satellite imageries were used as master and slave for each of these four major earthquakes. The spatio-temporal distribution of the ground deformation was analyzed using a zonal statistics algorithm in GIS. It focused on the overlapping area between the raster layer of the deformation map and the polygon layer of six observation sites (Mataram City, Pamenang, Tampes, Sukadana, Sembalun, and Belanting). The results showed that the deformation includes uplift and subsidence. The first 6.4 Mw foreshock hitting on 29 July 2018 produces a minimum uplift effect on the island. The 7.0 Mw mainshock on 5 August 2018 causes extreme uplift at the northern shore. The 6.2 Mw Aftershock on 9 August 2018 generates subsidence throughout the study area. The final earthquake of 6.9 Mw on 19 August 2018 initiates massive uplift in the study area and extreme uplift at the northeastern shore. The highest uplift reaches 0.713 m at the northern shore, while the deepest subsidence is measured −0.338 m at the northwestern shore. Dominant deformation on the northern area of Lombok Island indicates movement of Back Arc Trust in the north of the island. The output of this study would be valuable to local authorities to evaluate existing earthquake’s impacts and to design mitigation strategies to face earthquake-induced ground displacement.

Indonesia is exposed to earthquakes, volcanic activities, and associated tsunamis. This is particularly the case for Lombok and Sumbawa Islands in West Nusa Tenggara, where evidence of tsunamis is frequently observed in its coastal sedimentary record. If the 1815 CE Tambora eruption on Sumbawa Island generated a tsunami with well-identified traces on the surrounding islands, little is known about the consequences of the 1257 CE tremendous eruption of Samalas on the neighboring islands, and especially about the possible tsunamis generated in reason of a paucity of research on coastal sedimentary records in this area. However, on Lombok Island, the eruption of the Samalas volcano produced significant volumes of pyroclastic flows that entered the sea in the North and East of the island. These phenomena must have produced a tsunami that left their traces, especially on Sumbawa Island, whose western coastline is only 14 km away from Lombok’s eastern shore. Therefore, the main goal of this study is to investigate, find evidence, and determine the age of marine-origin sediments along the shore of the Alas Strait, Indonesia. We collected and analyzed samples of coral and seashells from marine deposits identified along the west coast of Sumbawa, i.e., in Belang Island and abandoned fishponds in Kiantar Village, in order to identify the sources and the occurrence period of these deposits events. Based on the radiocarbon dating of coral and seashell samples, we concluded that none of the identified marine deposits along the western coast of Sumbawa could be related chronologically to the 1257 CE eruption of Samalas. However, possible tsunami deposits located in Belang Island and abandoned fishponds in Kiantar Village yielded 4th century CE, 9th century CE, and 17th century CE. We also conclude that past large earthquakes triggered these tsunamis since no known volcanic eruption occurred near the Alas Strait at that time that may have triggered a tsunami.

ABSTRAK Perubahan pemanfaatan lahan pasca erupsi menyebabkan perubahan aktivitas perekonomian masyarakat, terutama untuk pemanfaatan lahan pertanian. Tujuan penelitian ini adalah : (1). Mengidentifikasi dampak erupsi Merapi 2010 terhadap perubahan pemanfaatan penggunaan lahan; (2). Menganalisis dampak perubahan pemanfaatan penggunaan lahan terhadap aktivitas perekonomian (matapencaharian) masyarakat setempat; (3). Mengevaluasi dan merekomendasi upaya pemulihan ekonomi masyarakat pasca erupsi. Perubahan penggunaan lahan diperoleh dari overlay Peta Penggunaan Lahan Sebelum Erupsi dengan Peta Penggunaan Lahan Sesudah Erupsi. Analisa daya pulih rumahtangga diperoleh dari wawancara. Penyamplingan dilakukan di Dusun dengan purposive sampling, mempertimbangkan daerah tersebut termasuk di daerah terdampak total atau sebagian dan jumlah korban KK terbanyak dan sedikit. Pengambilan sampel di KRB 3 sebanyak 50 responden, KRB 2 sebanyak 30 responden, dan KRB 1 sebanyak 15 responden. Pengambilan responden di setiap Dusun menggunakan metode simple random sampling karena memperhatikan keragaman populasi yang relatif homogen. Variabel yang dianalisa meliputi asset, akses, dan aktivitas masyarakat. Jenis penggunaan lahan mengalami penambahan pascaerupsi yaitu penambahan shelter dengan luas 140,66 Ha. Penggunaan lahan yang berkurang luasanya adalah semak belukar 312,994 Ha, kebun 292,702 Ha, rumput 30,514, dan tegalan 2155,698 Ha. Sedangkan penggunaan lahan yang bertambah luasannya adalah pemukiman 2222,664 Ha, sawah irigasi 428,584 Ha, dan shelter 140,66 Ha. Tingkat daya pulih rendah lebih besar yaitu 65%, dan daya pulih tinggi sebesar 35%. Dari ketiga variabel asset, akses, dan aktivitas, variabel asetlah yang memiliki kontribusi berpengaruh lebih besar. ABSTRACT Gendol Watershed be a research location because this watershed is the most severely affected. Cangkringan was chosen as the focus area on this research because this area as one of the District in Sleman that located on the slopes of Mount Merapi and the resources was affected. The changing of land use after the eruption can changes the economic activity of the communities, particularly for agricultural. The aims of this research are: (1). Identify the impact of Merapi eruption in 2010 for land use changes, (2). Analyzing the impact of land use changes for economic activities (livelihood) on local community; (3). Evaluation and recommendation public economic recovery efforts after the eruption. The land use changes acquired from the result overlay of Land Use before eruption and Land Use after eruption. Analysis of household resilience derived from the interviews. Sampling area on Kepuhharjo Village, Wukirsari , Glagahharjo and Argomulyo because this area was the greatest affected area. Sampling this area was done with purposive sampling, considering this area included in the severely affected or partial. Respondents of KRB 3 are 50 respondents, KRB 2 are 30 respondents, and KRB 1 are 15 respondents. Respondents in each Village was choosen by simple random sampling method because the observed variability is relatively homogeneous population. Variables analyzed include the assets, access, and community activities. Type of land use have increased post-eruption is shelters area 140,66 Ha. Land use was reduced by bush 312.994 ha , farm 292.702 ha, grass 30.514, and field 2155.698 Ha. Land use was improved by settlement 2222.664 ha, 428.584 ha of irrigated rice fields, and shelter 140.66 Ha. The changing of land use on post-eruption has a positive and negative impact on societies. The positive side for some communities provide new livelihoods, and negative impact the public land could not be processed, many homes are destroyed and majority communities lost their occupation. Resilience of communities are in low classified 65 %. From the three variables, asset variables that have the largest contribution affect on resilience.

ABSTRAK Bantarkawung adalah salah satu kecamatan di Kabupaten Brebes yang sering terjadi bencana tanahlongsor. Oleh karena itu diperlukan pemetaan tingkat kerawanan dan kerentanan serta penilaian indeks kesiapsiagaan masyarakat. Tujuan dari penelitian ini adalah menentukan tingkat kerawanan, menentukan tingkat kerentanan, menilai indeks kesiapsiagaan masyarakat dan menganalisis hubungan tingkat kerawanan dengan nilai indeks kesiapsiagaan masyarakat terhadap bencana tanah longsor. ABSTRACT Bantarkawung is one of the sub distict in Brebes regency which has many landslide occurences. Therefore, it is necessary to map susceptibility and vulnerability and to value community preparedness index. The aims of this research were to determine landslide susceptibility, determine vulnerability of element at risk (people and settlement) based on susceptibility zone toward landslide disaster, valuate community preparedness index, and analize relationship between susceptibility and community preparedness index toward landslide disaster.

Java, the most densely populated island in Indonesia, is located on top of the most seismically active areas in Southeast Asia: the Sunda Megathrust. This area is frequently hit by strong earthquake. More than 3,300 M>5earthquakesoccurred between 1973-2014. The wide range of mountainous areas and high intensity of rainfall, make several part of the island one of the most exposed regions for coseismic landslides such as Baturagung area, the Southeast mountainous area of Yogyakarta Province. An integrated method between RS and GIS was used to conduct the vulnerability assessment due to the lack of the site specific slope instability analysis and coseismic landslides data. The seismic zonation of Baturagung area was obtained based on the analysis of Kanai attenuation. The geologic information was extracted using remote sensing interpretation based on the 1:100,000 geologic map of Yogyakarta and geomorphologic map of Baturagung area as well. The coseismic landslide hazard assessment has been estimated using scoring analysis in the GIS platform proposed by Mora and Vahrson (1993) with several modification. The accomplished coseismic landslide hazard map shows medium hazard coverage in the eastern areas, in the upper slope of Baturagung area, which consists of Semilir Formation. The result provides a distinct description of coseismic landslides hazard distribution in Batuaragung area. However, it should only be the preliminary assessment of the site specific investigation especially on valuable area or asset.

Java Island, the most populated island of Indonesia, is prone to landslide disasters. Their occurrence and impact have increased mainly as the result of natural factors, aggravated by human imprint. This paper is intended to analyse: (1) the spatio-temporal variation of landslides in Java during short term and long-term periods, and (2) their causative factors such as rainfall, topography, geology, earthquakes, and land-use. The evaluation spatially and temporally of historical landslides and consequences were based on the landslide database covering the period of 1981 – 2007 in the GIS environment. Database showed that landslides distributed unevenly between West Java (67 %), Central Java (29 %) and East Java (4 %). Slope failures were most abundant on the very intensively weathered zone of old volcanic materials on slope angles of 30O – 40O. Rainfall threshold analysis showed that shallow landslides and deep-seated landslides were triggered by rainfall events of 300 – 600 mm and > 600 mm respectively of antecedent rainfall during 30 consecutive days, and many cases showed that the landslides were not always initiated by intense rainfall during the landslide day. Human interference plays an important role in landslide occurrence through land conversion from natural forest to dryland agriculture which was the host of most of landslides in Java. These results and methods can be used as valuable information on the spatio-temporal characteristics of landslides in Java and their relationship with causative factors, thereby providing a sound basis for landslide investigation in more detail.

Within the last decades, Kathmandu Valley in Nepal has been characterized by rapid population growth and related urbanization processes, leading to environmental degradation, pollution and supply bottlenecks in the metropolitan area. Effects of climate change are now putting additional stress on the urban system. In our research in Kathmandu, we carried out community and household surveys to analyze community perception on climate change and climate-related disaster preparedness. For this purpose, three categories of communities, 12 in all, were surveyed and interviewed: Squatter settlements, agricultural villages, and traditional villages. All settlements are located close to main rivers and therefore especially exposed to floods and droughts, and in slope position also to landslides. As a main result, we can conclude that people are generally aware of climate change and its potential consequences, such as climate change-related disasters. However, in their daily lives, climate change does not play a significant role and most communities have not taken any adaptation measures so far.

Lahar has been applied as a general term for rapidly flowing, high-concentration, poorly sorted sediment-laden mixtures of rock debris and water (other than normal streamflow) from a volcano. Lahars are one of the most destructive phenomena associated with composite volcanoes, which are dominant in Java Island. Resulting deposits of lahar are poorly sorted, massive, made up of clasts (chiefly of volcanic composition), that generally include a mud-poor matrix. The aim of this research is threefold: to discuss the initiation of lahars occurrences, their dynamics, to assess the hazard and to analyse the deposition. Lahars are either a direct result of eruptive activity or not temporally related to eruptions. Syn-eruptive lahars may result from the transformation on pyroclastic flows or debris avalanches which transform to aqueous flows (e.g. at Papandayan in November 2002); They may be also generated through lake outburst or breaching (e.g. at Kelut in 1909 or 1966), and through removal of pyroclastic debris by subsequent heavy rainstorms. Post-eruptive lahar occurs during several years after an eruption. At Merapi, lahars are commonly rain-triggered by rainfalls having an average intensity of about 40 mm in 2 hours. Most occur during the rainy season from November to April. Non-eruptive lahars are flows generated without eruptive activity, particularly in the case of a debris avalanche or a lake outburst (e.g., Kelut). A lahar may include one or more discrete flow processes and encompass a variety of rheological flow types and flow transformations. As such, lahars encompass a continuum between debris flows and hyperconcentrated flows, as observed at Merapi, Kelut and Semeru volcanoes. Debris flows, with water contents ranging from 10 to no more than about 25% weight, are non-newtonian fluids that move as fairly coherent masses in what is thought to be predominantly laminar fashion. However, the relative importance of laminar versus turbulent regime is still debatable. Hyperconcentrated streamflows contain 25- to about 40%-weight-water; these flows possess some yield stress, but they are characteristically turbulent. Hazard-zone maps for lahar were produced for most of the the Javanese volcanoes, but these maps are on too small-scale to meet modern zoning requirements. More recently, a few large-scale maps (1/10,000 and 1/2,000-scale) and risk assessments have been completed for a few critical river systems at Merapi.

In this study, direct risk assessment was developed for various scenarios on the basis of hazard (e.g. spatial probability, temporal probability and magnitude class), vulnerability and estimating cost of road damage. Indirect risk assessment was derived from traffic interruption. The impact of landslide both direct and indirect impact were analyzed in the road segment 174. The research results show the highest direct impact of debris slide type of magnitude I located in the 20th mapping unit. The lowest direct impact of debris slide type of magnitude I can be founded in the 18th mapping unit. The direct impact of rock fall type of magnitude I which is located in the 6th mapping unit. Meanwhile, indirect impact which was caused by road blockage is Rp. 4,593,607.20 and Rp. 4,692,794.40 by using network analysis and community perception methods respectively. After class classification, road segment 174 is dominated by very low hazard, very low vulnerability and very low direct impact.

This research aims at identification of spatial plan zonation in rock fall prone areas. Research method applies hazard, vulnerability and risk analysis as an input for spatial modeling using Multi Criteria Evaluation (MCE). Research reveals that in Girimulyo is susceptible towards rock fall. In the last decades, there were 16 occurrences of rock fall that impacted to physical damages. Fortunately, such disaster did not cause any harm to human life. Therefore, research argue that physical vulnerability analysis can be analyzed, while social vulnerability cannot be analyzed further, since it had less data support. According to the research, there are more than 48 housing units located in hazard zone. Hence, local government should initiate structural mitigation to avoid further loss. Research also reveals that areas with high susceptibility will not directly consider as high risk zone, unless it has high vulnerability index. Example: areas along escarpment, where it has high susceptibility, but it has no element at risk in the area. Thereby, research tries to present zonation for prone hazard areas, using risk index. The result is quite representative, since possible areas to be developed is anywhere alongside road network. Indication of the area is produced from the multi criteria analysis. Multi criteria analysis is an essential method to combine spatial data and its attribute. Using such method requires more data input and expertise in justifying indicator to be selected.

Located approximately a hundred kilometres north of Java Subduction Zone, Java Island has a complicated geology and geomorphology. The north zone is dominated by the folded area, the centre is dominated by the active volcanic arc and the south of Java including the study area (Southeast part of Yogyakarta City), is dominated by the uplifted southern mountain. In general, the study area is part of the Bantul’s Graben. In the middle part of study area flows the Opak River, which is often associated with normal faults of Opak Fault. The Opak Fault is such a complex fault system which has a complex local fault which can cause worst local site effect when earthquakes occur. However, the geology map of Yogyakarta is the only data that gives the characteristics of Opak Fault roughly. Thus, the effort to identify unchartered fault system needs to be done. The aims of this study are to conduct the outcrop study, to identify the micro faults and to improve the understanding of faults system to support the earthquake hazard and risk assessment. The integrated method of remote sensing, structure from motion (SfM), geographic information system (GIS) and direct outcrop observation was conducted in the study area. Remote sensing was applied to recognize the outcrop location and to extract the nature lineament feature which can be used as fault indicator. The structure from motion was used to support characterising the outcrop in the field, to identify the fault evidence, and to measure the fault displacement on the outcrops. The direct outcrop observation is very useful to reveal the lithofacies characteristics and to reconstruct the lithostratigraphic correlation among the outcrops. Meanwhile, GIS was used to analyse all the data from remote sensing, SfM, and direct outcrop observation. The main findings of this study were as follows: the middle part of study area has the most complicated geologic structure. At least 56 faults evidence with the maximum displacement of 2.39 m was found on the study area. Administratively, the north part of Segoroyoso Village, the middle part of Wonolelo Village, and the middle part of Bawuran village are very unstable and vulnerable to the ground motion amplification due to their faults configuration. The further studies such as geo-electric survey, boreholes survey, and detail geological mapping still need to be conducted in the study area to get better understanding of Opak Fault. Additionally, the carbon testing of charcoal that found in the outcrop and identification of exact location of the ancient eruption source also need to be done.

A detailed study had been conducted on the sediment of Mount Samalas’ volcanic eruption in 1257 AD. Using the framework of the reconstruction of the ancient eruption of Mount Samalas, the first step was to map and analyze the deposits of volcanic sediment. Secondly, we analyzed the effect of geomorphology and the distance function to the isopach thickness. The results show that a combination of methods allowed to provide a high resolution map of the distribution of the thickness of the volcanic deposits, both on the slope and in alluvial areas. Geo-electric survey results (both Vertical Electric Sound (VES) and 2D mapping) show consistent changes in the pattern of contrast resistivity layer interface, for all areas. The pattern changes in a row of the top layer, the high resistivity turned into the low. Furthermore, the second and third layer interface changes from low to the high resistivity. High resistivity on the top layer is interpreted as a layer of unconsolidated volcanic sediment. High resistivity values are range from 736 to 2000 Ohm.m on the top layer in the area of the slopes while in the area of alluvial, the resistivity values range from 20 to 958 Ohm.m. Generally, the volcanic deposits in the area of the slopes have a higher value of isopach (>17 m) than in areas of alluvial (