Construction of Gravity anomaly map in whole Peru

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We proposed a joint study for the processing of gravity data which were accumulated by the Instituto Geofisico del Peru (IGP) over the last 40 years. The primay objectives of this project is to carry out various researches by both Japanese and Peruvian participants in order (a) to check the correctness of IGP gravity data sets from the most basic level, (b) to repeat gravity measurements to obtain accurate data which can be used as the reference values, (c) to perform field surveys to obtain new gravity profiles over tectonically interesting areas, and (d) to compile all the available data into a Bouguer anomaly map of Peru and publish the map from IGP.We obtained the original readings of the gravity surveys of IGP from the field notes and digitized them completely. Using the constant tables for individual gravimeters, we tried to calculate gravity values for each measurement. Because of very unsatisfactory results as evaluted by the consistency with the values measured by us in 1980 or 1984, we remeasured the gravity values at many points in Peru to use them as the reference when the gravity data reduction is carried out. Thus we determined each gravity values of IGP data set using least suares method.Terrain correction was made using DTM3 digital terrain model which covered whole South America. DTM3 has 3'x3' precision and we interpolated them to apply terrain correction program which is used in Japan with KS-110 terrain models having 250m x 250m precision.Finally we constructed a new Bouguer anomaly map over the whole Peru with terrain corrections. This is the very first Bouguer Anomaly map over the Peruvian Andes using revised IGP gravity data. This map and revised IGP gravity data are very important towards the understandings for the mountain building process of Pervian Andes.