GEODETIC STRAIN ANALYSIS OF EASTERN INDONESIA BASED ON GPS DATA IN 2010-2018

• Main Author: Rahmadani, Suchi
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/48434
• Institution: Institut Teknologi Bandung

Eastern Indonesia is the region with the most complex tectonic conditions in Indonesia. This region is an area of interaction between four active plates, namely the Australian Plate, Pacific Plate, Philippine Sea Plate, and the Sunda Block. The present study aims to determine the potential of earthquake hazards in the study area by analyzing the current deformation zones in Eastern Indonesia. We have constrained the location of deformation zones, which can be interpreted as block and plate boundaries, proceeding from the continous geodetic strain analysis, such as dilatation rates, maximum shear strain rates, principal strain rates, second invariant rates, and rotation rates. The continuous strain rate is converted from the results of spline interpolation to GPS (Global Positioning System) speeds. Spline interpolation is applied to the latitude and longitude components of the geodetic velocity data with a grid size of 30 × 30 km (~ 0.3 degrees). GPS data used is based on observations of 44 continuous stations and 61 campaign stations of Global Positioning System (GPS) from 2010 to 2018. Principal strain rate estimation gives a range of values of 0.065-0.33 microstrain/year and -0.299-(-0.003) microstrain/year for extension and shortening components, respectively. The largest extension pattern is seen in the northern part of Papua, while the biggest shortening is seen in the North Flores area. From the maximum shear strain rate pattern, the area that experiences the biggest shear is around the Cendrawasih Bay and Nabire City in Papua (~0.295 microstrain/year). This fact is in line with the mapping of earthquake sources by the National Earthquake Study Center which estimates in the area that there are several shear faults with a slip rate of 17-35 mm/year (Cendrawasih Fault, Randawa Fault, and Wapoga Fault). Regions with high dilatation rates (~|0.3| microstrain/year) are located around the cities of Sorong in West Papua, Nabire, Jayapura and Membramo in Papua, and Bima in East Nusa Tenggara. The dominant shortening patterns occur in the Banda Sea, Flores, and Central Papua (Jawawijaya Mountains) region, this is due to the presence of a rising fault structure in the area. The pattern of dilatation shortening in North Flores shows that this area is accumulating energy that has the potential to produce earthquakes in the future. The next result of strain analysis is the estimation of the second invariant rate (strain magnitude). Second invariant rate represents that the more eastward, the greater the strain magnitude, with a range of 0-0.42 microstrain/year. North Flores, Banda Sea, Bird's Neck Papua, Cendrawasih Bay, and Jayapura have the greatest strain magnitude compared to other regions in Eastern Indonesia (> 0.15 microstrain/year). While the rotation rate pattern estimated from the geodetic tensor indicates that the Eastern Indonesia region does not rotate in a single rigid body. The pattern shows that Eastern Indonesia is dominated by clockwise rotation but with varying values. The greatest clockwise rotation rates are seen in the Membramo and Halmahera areas. Whereas counter clockwise rotations occur in the Timika area, Manokwari, and Bima. This is in line with previous research which states that the area is divided into several tectonic blocks, namely MS: Molucca Seas, BS: Banda Sea, BH: Bird's Head, MO: Maoke, TI: Timor.