Construction of Gravity anomaly map in whole Peru

我们提议对秘鲁地球物理研究所在过去40年中积累的重力数据进行联合研究。该项目的主要目标是由日本和秘鲁的参与者进行各种研究，以便（a）从最基本的层面检查国际重力测量计划重力数据集的正确性，（B）重复进行重力测量，以获得可用作参考值的准确数据，（c）进行实地调查，以获得地质构造感兴趣地区的新重力剖面，（d）将所有可获得的数据汇编成秘鲁的布格异常图，并从IGP出版。我们使用各个重力仪的常数表来计算每次测量的重力值。由于与1980年或1984年测得的重力值的一致性评价结果很不理想，我们在秘鲁的许多点重新测量了重力值，以便在进行重力数据整理时作为参考。利用最小二乘法确定了IGP数据集的各重力值，并利用覆盖整个南美洲的DTM 3数字地形模型进行了地形校正。DTM 3的精度为3“× 3”，利用日本KS-110地形模型（精度为250 m × 250 m）进行地形校正，最后建立了新的秘鲁布格异常图。这是秘鲁安第斯山脉上第一幅使用修订的IGP重力数据绘制的布格异常图。这幅图和修正后的IGP重力资料对理解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.