Strain analyis in Banda Sea using grid strain based on GPS observation

Abstract

Eastern Indonesia has very high deformation due to tectonic activity in triple junction area. Convergencing between plate in Eastern Indonesia trigger some microblocks. Tectonic block as one of deformation phenomenom due to the interaction of between plates can be understood by using strain analysis. Strain analysis shows the change of position, shape and dimension from an object. This research use 80 GPS from previous study by Koulali et al, (2015) and 7 continuous GPS in Bird’s Head to calculate strain rates in order to find relation between tectonic activity and strain rates in Banda Sea, and to identify block boundary. The GPS data are calculated using GAMIT/GLOBK software to obtain time series in each station. Strain rates are calculated using softwae package named grid strain which calculate strain based on interpolation using discretized geodetic measurement resulting strain rates in grid system. The data distribution and algorithm in grid strain influence the result of strain rates from grid strain. The result from strain calculation is in ranges −16,421×10−8 to −0,194×10−8 for shortening parameter and 1,653×10−8 to 18,92×10−8 for extension parameter. From strain analysis known that strain rates can identify tectonic activity but not accurately for block boundary. Banda Block, Timor Block, and Bird’s Head Block has different strain pattern especially in their boundary. Timor and eastern part of Banda Block dominated by shortening according to the back arc located in there, meanwhile western part of Banda Block and mostly of Bird’s Head dominated by very low shortening according to collision between Eurasia and Australia Plates. For further analysis need some additional data such as density of GPS sites, sesimicity, and gravity data.