Illustrate mud-fluid conduits and their variety using resistivity image profiling method in Southwest Taiwan

Abstract

We conducted 2D resistivity survey along nine survey lines and inverted them to 3D model by combining 2D data in the Gunshuiping mud volcano in order to understand: (1) the relationship between the resistivity image and the mud-fluid distribution, and (2) the influences of earthquakes and typhoon on mud volcanoes. The three long survey lines passed through the four craters, out of which one was active during the survey period; and the six short networked lines surrounded the crater 2 (C2). The results reveal that a vertical structure is present beneath crater 3 (C3), whom we interpret a conduit transporting the mud-fluid onto the near surface. Also, an area with low resistivity (less than 4 ohm-m) is found at a certain depth suggesting to be the mud-fluid chamber. The high resistivity (more than 4 ohm-m) distribution is found near the surface, and we suggest that the mud volcano craters communicate with each other by the 3D model. Moreover, after the Meinong earthquake of 6 February 2016, the resistivity rose obviously within about 10 m under the surface; while the resistivity of the mud-fluid conduits declined. We also found that after the earthquake, the original active crater (C3) had stopped and was replaced by another crater (C1). We inferred that when the earthquake happened, the gases escaped to the surroundings and caused the gas content of the shallow surface to increase. Besides, as the original crater collapsed, the gases needed another crack to release, which made another crater re-activate. The data also shows that after the typhoon, the resistivity of mud-fluid conduits rose with the active crater changed again from C1 to C4.