| Summary: | Gravity and magnetic surveys were conducted at a part of the Rembang Keodeng depression zone, in July and August 2005, by academic staff members and students of the Gadjah Mada University Geophysics Study Program. The survey area covers the Kudus, Juwana, Pati, and Grobogan sub provinces in Central Java. Comprehensive and systematic data reduction, correction, and analysis, including upward continuation to a horizontal plane were applied to 145 data points with 1 km average spacing measured by both gravity and magnetics. Differential global positioning was used to determine location and elevation. In addition, reduction to the magnetic pole and pseudo-gravity transformation were applied to the magnetic data A normal fault with 1.15 km throw and 30 km length is modeled using Grav2D software based on the Talwani method. The lower part of the faulted sedimentary section has been buried by 0.5 km of alluvium. The magnetic anomaly is still dominated by a strong positive regional field The model represents only a small part of the Lasem and Pati faults within the Kendeng - Rembang depression system. The modeling also indicates an anticline syncline system (i.e. anticlinorium) at a depth of about 11-13 km beneath the survey area
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