The Southeast of Yogyakarta City has had the heaviest damages to buildings in the 2006 of Yogyakarta Earthquake disaster. A moderate to strong earthquake of 6.3 Mw shook the 20 km southeast part of the Yogyakarta City early in the morning at 5:54 local time. On top of extensive damage in Yogyakarta and Central Java, more than 5700 people perished; 37,927 people were injured in the collapse of more than 240,396 residential buildings. Furthermore, the earthquake also affected the infrastructure and local economic activities. The total damages and losses because of the earthquake was 29.1 trillion rupiahs or equal to approximately 3.1 million US dollar. Two main factors that caused the severe damages were a dense population and the lack of seismic design of residential buildings. After reconstruction and rehabilitation, the area where the study was conducted grew into a densely populated area. This urbanistic change is feared to be potentially the lead to a great disaster if an earthquake occurs again. Thus, a comprehensive study about building vulnerability is absolutely needed in study area. Therefore, the main objective of this study has been the provision of a probabilistic model of seismic building vulnerability based on the damage data of the last big earthquake. By considering the relationship between building characteristics, site conditions, and the damage level based on probabilistic analysis, this study can offer a better understanding of earthquake damage estimation for residential building in Java. The main findings of this study were as follows: The most vulnerable building type is the reinforced masonry structure with clay tile roof, it is located between 8.1-10 km of the epicentre and it is built on young Merapi volcanic deposits. On the contrary, the safest building type is the houses which has characteristics of reinforced masonry structure, asbestos or zinc roof type, and being located in Semilir Formation. The results showed that the building damage probability provided a high accuracy of prediction about 75.81%. The results explain the prediction of building vulnerability based on the building damaged of the Yogyakarta earthquake 2006. This study is suitable for preliminary study at the region scale. Thus, the site investigation still needs to be conducted for the future research to determine the safety and vulnerability of residential building.

Indonesia is one of the most earthquake prone countries in the world. More than 14,000 earthquakes of magnitude greater than 5 occurred in Indonesia between 1897 and 2009. Earthquakes are a major cause of slope instability eventually triggering coseismic landslides, which cost 1.5 million US$/ year in Java: one of the most densely islands in Indonesia. This paper aims to assess coseismic landslide susceptibility using Geographic Information System (GIS) on the western flank of Baturagung Escarpment, 8 km southeast of the Yogyakarta City, a data sparse area. Therefore, we have used a probabilistic seismic hazard analysis to calculate the peak ground accelerations, while the coseismic landslide susceptibility analysis was done by the scoring method in the GIS adopted from Mora and Vahrson model (Costa Rica), which is well adopted for data sparse areas. The west flank of Baturagung Escarpment is dominated by moderate level of coseismic landslide with an average Coseismic Landslide Susceptibility Level (CLSL) of 33–162. The upper slope of Baturagung Escarpment, which consists of Semilir Formation has the CLSL of 163–512, corresponding to medium level CLSL (Mora and Vahrson model). The low level CLSL is mainly located on the foot slopes of Baturagung Escarpment, while the alluvial and colluvial plains located along the Opak River have very low CLSL (0–6). Based on the mapped landslide occurrence, the landslides tend to occur in the zone of moderate CLSL and they are distributed along the border between moderate and low coseismic landslide zone, meaning that the change on local condition could be playing an important role in triggering coseismic landslide.

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.

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.

The Pacitan Regency is at risk of megathrust earthquakes and tsunamis due to the seismic gap along the southern region of Java Island, making risk-reduction efforts crucial. This research aims to analyse the tsunami risk associated with a potential megathrust earthquake scenario in Pacitan’s coastal areas and develop sustainable mitigation strategies. The research employs spatial analysis to evaluate the risk and subsequently formulate strategies for long-term mitigation. A weighted overlay method was utilised to integrate hazard (H) and vulnerability (V) datasets to produce a tsunami risk map (R). The hazard component was modelled using a tsunami propagation simulation based on the Shallow Water Equations in the Delft3D-Flow software, incorporating an earthquake scenario of Mw 8.8 and H-loss calculations in ArcGIS Pro 10.3. The vulnerability assessment was conducted by overlaying population density, land use, and building footprint from the Global Human Settlement Layer (GHSL) datasets. Finally, sustainable strategies were proposed to mitigate the tsunami risk effectively. The results show that Pacitan faces significant tsunami disaster risk, with tsunami waves at the coast reaching 16.6 m. Because the coast of Pacitan is densely populated, mitigation strategies are necessary, and in the present contribution, the authors developed holistic spatial planning, which prioritise the preservation and restoration of natural barriers, such as mangroves and coastal forests.

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.