A Study of Complex Substructures in a Foothill Belt of Northwestern Taiwan Using Two-Dimensional Gravity Multiple-Source Model Inversion

Abstract

The goal of this pa per is to im prove the ca pa bil ity of grav ity in ver sion as sess ment of com plex struc tures us ing a mul ti ple-source model as in di cated by a study of a foot hill belt of north west ern Tai wan. In this study, a grav ity in ver sion com puter pro gram is ap plied based on re search de vel oped by Tsai, which con tains a Marquardt in ver sion al go rithm for math e mat i cal cal cu la tions and in cor po rates con straints on geo log i cal pa ram e ters. The com puted and mod i fied geo log i cal pa ram e ters are trans formed into co or di nates. The re sponse of a proper geological model is calculated using the Talwani technique. The method is ap plied to a field ex am ple in a foot hills belt of Tai wan that pos sesses com plex subsurface struc tures. The den sity pro file from 2D grav ity data, ob tained us ing our in ver sion com puter pro gram, re veals a good cor re la tion with the geo log i cal model ob tained from seis mic, bore hole, and geo logic data. Fur ther more, po ten tial hy dro car bon traps as so ci ated with some of the in ter preted geo log i cal struc tures (where no seis mic data are avail able) in the east ern and west ern seis mic sec tions are be ing eval u ated and as sessed for pos si ble fu ture de vel op ment. This pro file high lights fea tures that are im por tant to a good un der stand ing of an area with com plex subsurface struc tures. It also helps to de fine subsurface ge ol ogy and as sess po ten tial hy dro car bon traps. This two-di men sional mul ti ple-source model grav ity in ver sion algorithm provides a powerful tool to interpret the gravity data in this study.