Construction of Gravity anomaly map in whole Peru

我们提出了一项联合研究，用于处理秘鲁地质研究所（IGP）过去40年积累的重力数据。该项目的主要目标是由日本和秘鲁参与者进行各种研究，以便(a)从最基本的层面检查IGP重力数据集的正确性，(b)重复重力测量以获得可作为参考值的准确数据，(c)进行实地调查以获得构造感兴趣地区的新重力剖面。(d)将所有可用数据汇编成秘鲁布格异常图，并从IGP发布该地图。我们从现场记录中获得了IGP重力测量的原始读数，并将其完全数字化。使用单个重力仪的常数表，我们试图计算每次测量的重力值。由于与我们1980年或1984年的测量值的一致性评估结果非常不理想，我们重新测量了秘鲁许多点的重力值，以便在进行重力数据缩减时作为参考。因此，我们利用最小二乘法确定了IGP数据集的各重力值。采用覆盖整个南美洲的DTM3数字地形模型进行地形校正。DTM3具有3‘x3’精度，我们将它们插值到日本使用的地形校正程序中，使用精度为250m x 250m的KS-110地形模型。最后，通过地形校正，在整个秘鲁建立了新的布格异常图。这是秘鲁安第斯山脉上的第一张布格异常图，使用了修订的IGP重力数据。该地图和修正后的IGP重力资料对认识秘鲁安第斯山脉的造山过程具有重要意义。

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.