Application of gravity method for local geological structures identification in Surabaya

Geodetic study using Global Positioning System (GPS) has been done against the measurement of surface deformation in Java. Fault Kendeng is an active fault that extends from the eastern part of Java East to the western part of Central Java. The Java region obviously had a larger density difference because subduction rate is higher. This study indicated a new major earthquake will threat through East Java and causes tsunami to Bali, Lombok, Nusa Tenggara, and other beaches along the Flores Sea. Geological sheet of Surabaya showed the area of Surabaya and its surrounding are traversed by several structures geology liked the Lidah and Kedung Waru active faults which are associated with Lidah Anticline, Gayungan Anticline and Kedung Waru Anticline. Therefore, Surabaya and its surrounding areas had the potential of an earthquake. The measurement with gravity method can describe the condition of the structure under the surface which includes the interpretation of lithology as well as identify the presence of fault in the city of Surabaya. This study will become additional information for mitigation efforts and reviewing the spatial plan and territory in Surabaya.