Heri Andreas

CRUSTAL DEFORMATION STUDIES IN JAVA (INDONESIA) USING GPS

Along the Java trench the Australian–Oceanic plate is moving and pushing onto and subducting beneath the Java continental crust at a relative motion of about 70 mm/yr in NNE direction. This subduction-zone process imposed tectonic stresses on the fore-arc region offshore and on the land of Java, thus causing the formation of earthquake fault zones to accommodate the plate movement. Historically, several large earthquakes happened in Java, including West Java. This research use GPS surveys method to study the inter-seismic deformation of three active faults in West Java region (i.e. Cimandiri, Lembang and Baribis faults), and the co-seismic and post-seismic deformation related to the May 2006 Yogyakarta and the July 2006 South Java earthquakes. Based on GPS surveys results it was found that the area around Cimandiri, Lembang and Baribis fault zones have the horizontal displacements of about 1 to 2 cm/yr or less. Further research is however still needed to extract the real inter-seismic deformation of the faults from those GPS-derived displacements. GPS surveys have also estimated that the May 2006 Yogyakarta earthquake was caused by the sinistral movement of the (Opak) fault with horizontal co-seismic deformation that generally was less than 10 cm. The post-seismic horizontal deformation of the July 2006 South Java tsunami earthquake has also been estimated using GPS surveys data. In the first year after the earthquake (2006 to 2007), the post-seismic deformation is generally less than 5 cm; and it becomes generally less than 3 cm in the second year (2007 to 2008).

Land subsidence in coastal city of Semarang (Indonesia): characteristics, impacts and causes

Semarang is the capital of Central Java province, located in the northern coast of Java island, Indonesia. Land subsidence in Semarang has been widely reported and its impacts can be seen already in daily life. Based on the estimation from Levelling, Interferometric Synthetic Aperture Radar (InSAR), Microgravity and Global Positioning System (GPS) survey methods, land subsidence with rates of up to about 19 cm/year were observed during the period of 1999 up to 2011. Results derived from GPS since 2008 up to 2011 show that land subsidence in Semarang has spatial and temporal variations, with spatial average rates of about 6 to 7 cm/year and maximum rates that can go up to 14–19 cm/year at certain locations. The northern region of Semarang along the coast exhibits higher rates of subsidence compared to its southern region, and this subsidence is believed to be caused by the combination of natural consolidation of young alluvium soil, groundwater extraction and load of buildings and constructions. The impact of land subsidence in Semarang can be seen in several forms, mainly the wider expansion of (coastal) flooding areas, cracking and damage of buildings and infrastructure, and increased inland sea water intrusion.

STUDYING LAND SUBSIDENCE OF BANDUNG BASIN (INDONESIA) USING GPS SURVEY TECHNIQUE

Abstract Bandung basin is a large intra-montane basin surrounded by volcanic highlands, inhabited by more than five million people. Based on four GPS (Global Positioning System) surveys conducted on February 2000, November 2002, July 2002 and June 2003, it can be concluded that in the period of 2000 to 2003 several locations in Bandung basin have experienced land subsidence. In this period of about 3 years, land subsidence in a few locations can reach the amount of 40 to 50 cm, with the speed of about 1-2 cm/month. This paper describes the technical and practical aspects of GPS surveys for land subsidence study in Bandung basin along with the obtained results. This study shows that the amount of land subsidence in several locations of Bandung basin do not show significant correlation with the registered abstraction volume of groundwater in that locations. Paper will sum up with some conclusions and recommendations.

On the Roles of Geospatial Information for Risk Assessment of Land Subsidence in Urban Areas of Indonesia

Land subsidence is a silent hazard that may occurs in large urban areas, and usually caused by combination of excessive groundwater extraction, natural consolidation of alluvium soil, load of constructions and tectonic activities. Geospatial information is useful for studying the characteristics, causes, impacts and cost of land subsidence. This paper concentrates on the roles of geospatial information for risk assessment of land subsidence in three large cities in Indonesia, namely Jakarta, Bandung and Semarang. Geodetic based results show that land subsidence rates in all three cities generally have spatial and temporal variations, and their magnitude is in average about 5–10 cm/year and can reach up to about 20 cm/year at certain locations and times. The impact of land subsidence can be seen already in the field in forms of the buildings and infrastructure cracking, the wider expansion of (coastal) flooding areas, and increased inland sea water intrusion. Land subsidence has a strong linkage with urban development process. Urban development increases the built-up areas, population, economic and industrial activities, and also groundwater extraction, which can then lead to land subsidence.

Monitoring Land Subsidence of Jakarta (Indonesia) Using Leveling, GPS Survey and InSAR Techniques

Jakarta is the capital city of Indonesia with a population of about 12 million people, inhabiting an area of about 25-km by 25-km. It has been reported for quite sometime that several locations in Jakarta are subsiding at different rates. Leveling surveys performed in 1982, 1991 and 1997 have detected the subsidence up to about 80 cm during the period of 1982–1991, and up to about 160 cm during the 1991–1997 period; while GPS surveys observed the subsidence up to about 50 cm during the period of 1997–2002. InSAR technique using JERS-1/SAR L-band data estimated a subsidence rate of about 5 to 10cm during the period of 1993 to 1995. Maximum subsidence were found in the northwestern and central eastern parts of Jakarta, while minimum subsidence were found in the southern part. InSAR results show good correspondence with the results from Leveling and GPS Surveys

Combined X- and L-band PSI analyses for assessment of land subsidence in Jakarta

Jakarta is the capital of Indonesia and is home to approximately 10 million people on the coast of the Java Sea. The subsidence due to groundwater extraction, increased development, natural consolidation of soil and tectonics in Jakarta has been known since the early part of the 20th century. Evidence of land subsidence exists through monitoring with GPS, level surveys and preliminary InSAR investigations [1]. World Bank studies conservatively estimate land subsidence in Jakarta occurring at an average rate of 5 cm per year, and in some areas, over 1 meter was already observed. Recent studies of land subsidence found that while typical subsidence rates were 7.5-10 cm a year, in localized areas of North Jakarta subsidence in the range 15-25 cm a year was occurring, which if sustained, would result in them sinking to 4 to 5 meters below sea level by 2025. Land subsidence will require major interventions, including increased pumping, dikes and most likely introducing major infrastructure investment for sea defence [1]. With the increasing prevalence of Earth Observation (EO), the World Bank and the European Space Agency (ESA) have set up a partnership that aims at highlighting the potential of EO information to support the monitoring and management of World Bank projects. It in this framework that was defined the EOWorld projects [2]. Altamira Information, company specialized in ground motion monitoring, has managed one of those projects, focusing on the assessment of land subsidence in Jakarta.

On the establishment and implementation of GPS CORS for cadastral surveying and mapping in Indonesia

Abstract Since 2009, the latest satellite based positioning system in the form of global positioning system (GPS) continuously operating reference station (CORS) has been tested to support cadastral surveying and mapping in Indonesia, specifically in Java and Bali islands. The main aim of this GPS CORS implementation is to speed up the land registration process in Indonesia. Currently about 55% of land parcels are still to be certificated (e.g. about 48 million parcels), and about 90% of the area are still to be mapped for cadastral purposes (e.g. about 83 million ha). At present in 2013, there are 183 GPS CORS stations have been established for this purpose by the National Land Agency of Indonesia (BPN). In establishing, operating and maintaining a good and reliable GPS CORS network that can serve cadastral surveying and mapping all over Indonesia, there are several challenges and constraints that have to be properly taken into consideration mainly related to: integration of several existing GPS CORS networks in Indonesia; expanding the coverage of GPS CORS to cover a vast region of Indonesia; availability and reliability of the communication link system; establishment of reliable GPS CORS data processing and management at BPN and district land offices; spatial and temporal variations in achievable accuracy of GPS CORS derived coordinates; insufficient number of dedicated and professional GPS CORS surveyors at BPN and all district land offices; and local social and political challenges. These challenges and constraints have to be effectively overcome to have meaningful implementation of GPS CORS in supporting cadastral surveying and mapping in Indonesia. This GPS CORS network will also serve other non cadastral applications in Indonesia.

Studying landslide displacements in the Ciloto area (Indonesia) using GPS surveys

The paper presents and discusses results and performance of GPS surveys in Ciloto, a well known landslide prone area in West Java (Indonesia). Five GPS surveys involving 17 GPS points have been conducted during the period 2002–2005. The results of the GPS surveys show that the magnitude of land movements in the study area vary from centimetres to decimetres, depending on the location and observation seasons. The study also suggests that to confirm the displacements of the GPS points and to infer the type of landslide, GPS estimated displacements should be tested and analysed with different methods.

Adaptation and mitigation of land subsidence in Semarang

Land subsidence is not a new phenomenon for Semarang. Some report said the subsidence in Semarang probably is occurring for more than 100 years. Based on the leveling surveys conducted by the Centre of Environmental Geology from 1999 to 2003 it was found that relatively large subsidence was detected around Semarang Harbor, Pondok Hasanuddin, Bandar Harjo and around Semarang Tawang Railway station, with the rates ranging from 1 to 17 cm/year. Results derived from GPS show that land subsidence in Semarang has spatial and temporal variations. In general, subsidence rates in Semarang have an average rate of about 6 to 7 cm/year, with maximum rates that can go up to 14-19 cm/year at certain locations. The impact of land subsidence in Semarang can be seen in several forms, such as the wider expansion of (coastal) flooding areas “rob”, cracking of buildings and infrastructure, and increased inland sea water intrusion. It also badly influences the quality and amenity of the living environment and life (e.g. health and sanitation condition) in the affected areas. In the case of Semarang, adaptation and mitigation are considered very important. We have been done some investigations to this area by field observations (mapping the flooded area, mapping the infrastructure problems, interviewing people and seeing the adaptations, conduct GPS measurement to see deformation, etc.), gather information from Government, from digital media, etc., and we noticed people increased their house, and the local goverment elevated the road and the bridge, etc. regulary over less decade periode as part of adaptation. We also noticed the Central Goverment built the dyke and pumping station. Our conclusions said that the adaptation only made temporaly since significant land subsidence keep coming and worsening by the sea level which is keep rising. Another conclusion, so far we have seen lack of mitigation program, monitoring or even inevective mitigation in Semarang related to this subsidence issue.Land subsidence is not a new phenomenon for Semarang. Some report said the subsidence in Semarang probably is occurring for more than 100 years. Based on the leveling surveys conducted by the Centre of Environmental Geology from 1999 to 2003 it was found that relatively large subsidence was detected around Semarang Harbor, Pondok Hasanuddin, Bandar Harjo and around Semarang Tawang Railway station, with the rates ranging from 1 to 17 cm/year. Results derived from GPS show that land subsidence in Semarang has spatial and temporal variations. In general, subsidence rates in Semarang have an average rate of about 6 to 7 cm/year, with maximum rates that can go up to 14-19 cm/year at certain locations. The impact of land subsidence in Semarang can be seen in several forms, such as the wider expansion of (coastal) flooding areas “rob”, cracking of buildings and infrastructure, and increased inland sea water intrusion. It also badly influences the quality and amenity of the living environment and life (e.g. healt...

Understanding the trigger for the LUSI mud volcano eruption from ground deformation signatures

Abstract The LUSI mud volcano in the sub-district of Porong, Sidoarjo, East Java, Indonesia started to erupt on 29 May 2006. An almost continuous eruption of a mixture of mud, water and gas has occurred around this area since this date. The eruption triggered vertical and horizontal ground deformation. From June 2006 to December 2010, 14 global positioning system campaigns were conducted to observe the ground deformation using c. 50 stations sparsely located up to 10 km from the eruption centre. Field observations of cracks, terrestrial laser scanning and geo-electrical measurements have also been used to infer the ground deformation signature around the LUSI mud volcano. More than 150 pairs of interferograms generated from 66 ALOS PALSAR images from June 2006 to December 2009 have also been used to study the ground deformation caused by the LUSI mud volcano. The LUSI mud eruption began only 200 m from where the Lapindo Inc. oil company was drilling for oil and gas. The drilling may have pierced a deeper high-pressure zone, causing an underground blow-out of the drillhole into a hydrofracture. Alternatively, the magnitude 6.3 Yogyakarta earthquake, which was located c. 275 km from the eruption site and occurred two days before the LUSI eruption, may have shaken the area sufficiently to cause the eruption by reactivating a fault in the region and liquefying the mud. These two hypotheses for triggering the mud volcano have been argued vehemently and still remain controversial. The ground deformation signatures provide important clues to understanding the trigger for the eruption and to solve this controversy. Co-seismic fault reactivation has its own typical ground deformation signature. This study used global positioning system and InSAR techniques, as well as field observations of cracks, terrestrial laser scanning and geo-electrical measurements, to determine the signature of ground deformation around the LUSI mud volcano and to explain the triggering mechanism.