ANALISA PERBANDINGAN ANOMALI GRAVITASI DENGAN PERSEBARAN INTRUSI AIR ASIN (STUDI KASUS JAKARTA 2006-2007)

Aplikasi pada bidang geofisika, berupa pengukuran gravitasi dilakukan di lapangan dalam jangka waktu tertentu, dengan tujuan untuk mendeteksi perubahan kondisi bawah permukaan bumi. Dalam hal ini dilakukan pengukuran gravitasi di wilayah Jakarta untuk mendeteksi perubahan kondisi hidrologi Jakarta dalam kaitannya dengan fenomena intrusi air asin. Secara geografis daerah penelitian berada pada -6.35158 s.d -6.08655 LS dan 106.689 s.d. 106.955 BT. Pengolahan data gravitasi wilayah Jakarta dilakukan dalam 2 periode, yaitu periode I (September 2006) dan periode II (November–Desember 2007). Anomali gravitasi  tertinggi terdapat pada bagian pusat dan barat Jakarta ini mengindikasikan terjadinya fenomena subsidensi dan kekosongan massa akibat eksploitasi air tanah serta tekanan dari sejumlah gedung tinggi yang berpusat pada daerah tersebut. Anomali gravitasi terendah terdapat di bagian barat laut Jakarta yang bersesuaian konsentrasi nilai kepayauan tertinggi, mengindikasikan adanya intrusi air asin yang diakibatkan oleh adanya fenomena Conate Water yang menyusup  pada aquifer air tanah akibat eksplotasi air tanah berlebih. Hubungan pola aliran sungai dengan nilai kepayauan air, membuktikan adanya pengaruh sungai aquifer air tanah, namun dampaknya tidak terlalu berpengaruh terlebih pada aquifer dalam.   Gravity measurements are conducted in the field within a certain period in order to detect changes in the earth's surface conditions. We conducted gravity measurements in Jakarta to detect changes in hydrologic conditions in connection to salt water intrusion phenomena. The data processing performed in the two periods, the first period is September 2006 and the second one is November-December 2007. The highest gravity anomalies are in central and western parts of Jakarta. This implies the occurrence of mass subsidence and void due to the exploitation of ground water and the pressure from a number of high buildings based on the area. The lowest gravity anomaly takes place in the northwest of Jakarta. This condition is corresponding to the highest concentrations and show that there is salt water intrusion. The intrusion caused by Connate water that infiltrated the groundwater aquifer due to ground water overexploitation. The relationship between river flow patterns and salt concentration show that there is influence of groundwater aquifer of the river, but the influence is insignificant to deep aquifer

Preserving past tsunami information for future preparedness in Indonesia and the Philippines

Recent tsunamis, especially after the 2004 Indian Ocean tsunami, provided a better understanding and knowledge of tsunami science as well as on how to build awareness and preparedness. However, tsunamis that happened before 2004, there is limited and/or scattered data, information, records, and reports of the events. In addition, there is either limited or no eyewitness’s story documented, including pictures and videos. The lack of information makes it difficult for policymakers, researchers, and other institutions to disseminate local and contextualized information to the public in raising awareness and education on disaster preparation and mitigation. If a tsunami has happened in the past, it is most likely to happen again in the future. It is imperative that we learn from the past and prepare for the future. This study aims to improve the knowledge of the impact of the tsunami in selected sites in Indonesia and the Philippines prior to 2004, through investigation of historical documents and archives, as well as documentation of eyewitness accounts. The result of this study is expected to be a more effective way to build awareness and to educate the local community. Having evidence-based of past tsunami event in the area will motivate stronger preparedness. It will also provide a better understanding to the local policymakers, disaster management agencies, as well as the community as it is based on local eyewitness accounts and other local sources, as opposed to using examples from other sites, districts, countries or regions

Preserving past tsunami information for future preparedness in Indonesia and the Philippines

Recent tsunamis, especially after the 2004 Indian Ocean tsunami, provided a better understanding and knowledge of tsunami science as well as on how to build awareness and preparedness. However, tsunamis that happened before 2004, there is limited and/or scattered data, information, records, and reports of the events. In addition, there is either limited or no eyewitness’s story documented, including pictures and videos. The lack of information makes it difficult for policymakers, researchers, and other institutions to disseminate local and contextualized information to the public in raising awareness and education on disaster preparation and mitigation. If a tsunami has happened in the past, it is most likely to happen again in the future. It is imperative that we learn from the past and prepare for the future. This study aims to improve the knowledge of the impact of the tsunami in selected sites in Indonesia and the Philippines prior to 2004, through investigation of historical documents and archives, as well as documentation of eyewitness accounts. The result of this study is expected to be a more effective way to build awareness and to educate the local community. Having evidence-based of past tsunami event in the area will motivate stronger preparedness. It will also provide a better understanding to the local policymakers, disaster management agencies, as well as the community as it is based on local eyewitness accounts and other local sources, as opposed to using examples from other sites, districts, countries or regions