Lembang Fault Research Articles

Special Issue on Multi-disciplinary Hazard Reduction from Earthquakes and Volcanoes in Indonesia

Natural disasters and their mitigation are global issues, especially in Asian countries, which have suffered from such geohazards as earthquakes, tsunamis, and volcanic eruptions and such hydrometeorological hazards as typhoons, cyclones, storm surges, and floods. Research on natural hazards and disasters is multidisciplinary. Scientists from a wide variety of disciplines study hazards, their causes, their mechanisms, and prediction. Engineers study infrastructures and measures to reduce vulnerability. Social and humanitarian scientists study cultural and societal aspects of disasters. Educators study effective ways to raise people’s awareness and action. In addition to such research activities, practitioners work to implement the results of scientific research into practical policymaking. This special issue of JDR contains 12 papers on multidisciplinary studies concerning geohazards in Indonesia taken from a Science and Technology Research Partnership for Sustainable Development (SATREPS) project supported by the Japan Science and Technology Agency (JST) and the Japan International Cooperation Agency (JICA). SATREPS projects focus on both the scientific aspect, namely, acquiring new knowledge, and the Official Development Aids (ODA) aspect, namely, implementing such knowledge in societal applications. Following the first review article, which is a project overview, the next four papers report findings on natural hazards – the slip rate on the Lembang fault in Java, tsunami simulation for Java’s Palabuhanratu, the Sinabung volcano eruption in Sumatra, and methods of predicting and evaluating eruptions. One paper reports engineering studies on tsunami disaster mitigation in Padang city and two social science papers present hazards in the contexts of communities and human mobility. Two papers on disaster education cover disaster education development since the 2004 Indian Ocean tsunami and the use of tsunami simulation in disaster education. The last research paper and review article deal with policymaking related to the 2010 Mentawai and 2011 Japan tsunamis, respectively. All of these papers, including the review articles, have been peer-reviewed by two nonproject reviewers. We thank the authors for their timely contributions and revisions, and the reviewers for their invaluable and wide-ranging comments.

Piping Flexibility Analysis of the Primary Cooling System of TRIGA 2000 Bandung Reactor due to Earthquake

Earthquakes in a nuclear installation can overload a piping system which is not flexible enough. These loads can be forces, moments and stresses working on the pipes or equipments. If the load is too large and exceed the allowable limits, the piping and equipment can be damaged and lead to overall system operation failure. The load received by piping systems can be reduced by making adequate piping flexibility, so all the loads can be transmitted homogenously throughout the pipe without load concentration at certain point. In this research the analysis of piping stress has been conducted to determine the size of loads that occured in the piping of primary cooling system of TRIGA 2000 Reactor, Bandung if an earthquake happened in the reactor site. The analysis was performed using Caesar II software-based finite element method. The ASME code B31.1 arranging the design of piping systems for power generating system (Power Piping Code) was used as reference analysis method. Modeling of piping systems was based on the cooling piping that has already been installed and the existing data reported in Safety Analysis Reports (SARs) of TRIGA 2000 reactor, Bandung. The quake considered in this analysis is the earthquake that occurred due to the Lembang fault, since it has the Peak Ground Acceleration (PGA) in the Bandung TRIGA 2000 reactor site. The analysis results showed that in the static condition for sustain and expansion loads, the stress fraction in all piping lines does not exceed the allowable limit. However, during operation moment, in dynamic condition, the primary cooling system is less flexible at sustain load, ekspansi load, and combination load and the stress fraction have reached 95,5%. Therefore a pipeline modification (rerouting) is needed to make pipe stress does not exceed the allowable stress. The pipeline modification was carried out by applied a gap of 3 mm in the X direction of the support at node 25 and eliminate the support at the node 30, also a gap of 3 mm was applied in X and Z directions of the support at the node 155. The axial force (FY) that occurred in the pump outlet nozzle (dia. 4 in.) of PriPump line have also exceeded the allowable limit that lead to the pump nozzle failure during an earthquake of Lembang fault. The modifications is necessary to be applied on the cooling system for PriPump line so the nozzle would not receive the force that exceed the allowable limits. The modification can be done by removing the support at node 105 and node 135 so the primary cooling system piping of Bandung TRIGA 2000 reactor would be safe to operate during an earthquake originated from Lembang fault. Received: 20 November 2010; Revised: 18 July 2011; Accepted: 20 July 2011

Structural geology controls on groundwater flow: Lembang Fault case study, West Java, Indonesia

Field evidence has shown that Lembang Fault (West Java, Indonesia) can act as a groundwater flow barrier. There are outcrops along the footwall comprising consolidated brecciated rock with very low permeability, springs and hot springs occurring along down-thrown hanging-wall rock adjacent to the fault, and a high permeability layer of old and young Tangkuban Parahu eruptive materials (hanging wall) juxtaposed against the low permeability of the older volcanic layer of Bukit Tunggul unit (footwall). Two different environmental tracers were utilized in the study: electrical conductivity measurement and stable isotope analysis. Hydraulic head was measured at some wells along the fault and water electrical conductivity measurements were carried out in a small catchment, the upper part of Cikapundung River basin, which is located just north of Bandung City. Water samples for stable isotope composition analysis were taken from 19 observation wells distributed randomly inside the basin. All analysis data lead to the recognition that Lembang Fault blocks the groundwater flow. No indication was found for water being recharged at higher elevation in the northern part of Bandung Basin, which means the recharged water in Mount Tangkuban Parahu area does not reach Bandung Plain.

A chronology for geomorphological developments in the greater Bandung area, West-Java, Indonesia

The greater Bandung area (West-Java, Indonesia) is a large intramontane basin surrounded by volcanic highlands. Geomorphological and sedimentological studies reveal that the morphology of the central basin and the Sunda-Tangkuban Perahu volcanic complex developed during the Middle-Late Quaternary, in particular since 125 kyr B.P. Tectonic subsidence, paroxysmal eruptions, volcanism-induced faulting/rifting, drainage system adaptations and intramontane lacustrine sedimentation (partly geomorphology-controlled) constitute the dominant landform-determining processes. A reconstruction of the regional morphological development is based on interpretation of morphological features and morphodynamic processes in the volcanic upland, in combination with analysis of the sedimentary record in the basin. A chronological framework is based on datings obtained from surficial sediments and deep drill cores. Initially, long term patterns in volcanicity and tectonic effects determine regional sedimentation and relief development in the greater Bandung area. Fluvial sedimentation and weathering prevailed in the basin, while the southern and northern volcanic ranges gradually formed. Basin subsidence, with contemporaneous volcanism around 125 kyr B.P., resulted in the formation of an enclosed intramontane basin, and stimulated lacustrine sedimentation. From this time on, concentration of volcanicity in the northern Sunda-Tangkuban Perahu complex and the resulting morphostructural developments caused rapid (catastrophic) and localized morphological changes. Cataclysmic eruptions (around 105 kyr B.P. and 50-35 kyr B.P.) caused voluminous sediment inflow in the northwestern basin. These events mark the significance of the Sunda-Tangkuban Perahu volcanic centre during the Late Quaternary; the Sunda volcano collapsed into a caldera in which later the Tangkuban Perahu volcano developed. Moreover, these eruptions controlled regional sedimentation and determined landform development in the greater basin area. In the vicinity of the eruption centre, volcano-tectonic faulting formed the conspicuous E-W Lembang fault that controlled distribution of volcaniclastic sediments and the initiation of a new drainage system in the Lembang area. In the low-lying Bandung plain persistent (fluvio)lacustrine and volcaniclastic sedimentation, followed by basin subsidence and minor fluvial erosion characterised the younger phases of landform development.