GEOLOGY AND SEISMICITY STUDY OF BENGKULU AND SURROUNDING AREA, CASE STUDY OF BENGKULU EARTHQUAKE IN 2007

• Main Author: Nopriawan
• Format: Final Project
• Language: Indonesia
• Subjects: Geologi, hidrologi & meteorologi
• Online Access: https://digilib.itb.ac.id/gdl/view/33583
• Institution: Institut Teknologi Bandung

This study is conducted in Bengkulu City and surrounding area, which is located in 3°44’19” S - 3°49’12” S and 102°16’12” E - 102°20’35” E. The objective of this research is to study the geological arrangement in Bengkulu and the distribution of damages that was caused by the earthquake on September 12th 2007, and also to correlate the damages that caused by the earthquake to geological condition of this research area. Geomorphologically, this study area consists of homoclinal hills, homoclinal valley, cuesta hills, intrusion hills, and coastal plain that were controlled by lithological type and structural geology. Geologically, the study area consists of Sandstone I Unit, Claystone Unit, Sandstone II Unit, Microdiorite Intrusion, Reef Carbonate Rocks, and Aluvial deposit. The Sandstone I Unit is the oldest rock in this research area. Lay on this unit is Claystone Unit that deposited conformably. Then there is Sandstone II Unit that deposited conformably lay on Claystone Unit. Those Units are equal to Simpangaur Formation that deposited in Pliocene. The activity of magmatism that activated in Late Pliocene resulted Microdiorite Intrusion. This activity was followed by uplift that resulted Reef Carbonate Rocks in Pleistocene. Aluvial deposit that deposited in every outcropped units is deposited unconformably. The geological structures that developed in this research area are faults that have orientation of NW-SE and fracture system that dominantly have orientation of NW-SE and NE-SW. The earthquake that happened on September 12th 2007 caused construction failures, land cracks, liquefaction, subsidence, and low intensity tsunami. The damages mainly happened in the area that geologically consisted of Quarternary sediment. The Quarternary sediment of this research area is a surface deposit that consists of unconsolidated loose materials that make the shaking from the earthquake become stronger. Intensity earthquake map that based on MMI scale (Modified Mercalli Intensity) give an illustration that the distribution of damages occurred at Lempuing, Padang Jati, Kandang Limun, Air Napal, Lais, Pantai Pasir Indah, Desa Serangai, Komplek Dolog, Pantai Pasar Bawah, Desa Muara Maras, and Pasar Seblat.