Temporal changes of complete bougeuer anomalies at Bromo Volcano, East Java, Indonesia

Bromo is one of the most active volcanoes located in Tengger Caldera, East Java, Indonesia. Historically, Bromo volcano was erupted about 50 times since 1775. Temporary gravity observation has been conducted at Bromo volcano in 1997, 2001 and 2014 to identified the temporal changes of Complete Bouguer Anomaly (CBA). The results of the research noted that for 17 years, subsurface conditions from Bromo volcano has changed. The changes in this period caused by volcanic activity from Bromo eruption, especially after eruption in 2000, 2004, 2010, and 2011. Based on the results of the gravity survey, Bromo volcano’s structure has changed both in terms of morphology as well as geologically. This temporal changed was identified in the value of CBA around Bromo volcano. The CBA data is representative to determine the dynamic of magma chamber beneath Bromo volcano. In 1997, CBA obtained with range from 200 to 620 mGal and in 2001, the CBA contour’s range is wider than 1997, that is from -320 to 120 mGal. The wide range affected by large distribution observed data with high vertical-horizontal topographic. The CBA 2014 distributed in the range of 454 to 496 mGal from 250 m and mean height as 350 m vertical topographic each datum.