The Possibly of the November-December 2018 earthquakes caused by hydrothermal in the Mamasa and surrounding areas derived by the earthquake relocation data

During the last two months in 2018, 761 earthquakes occur in Mamasa Region, west Celebes. These earthquakes are not lying in known active faults in Celebes and not have mainshock. About 287 earthquakes felt by local society. Mapping for detailed seismicity in this region is crucial to know the source of this earthquake sequence. The Inversion from arrival time catalog was performed to derive the 1-D local velocity model. The initial velocity model is obtained by combining ak135 for spherical average structure and local velocity model in Palu Koro Region that has been studied previously. The new local velocity model was used to compute double-difference relocation, while data input was arrival time catalog from Meteorological Climatological and geophysical agency. We successfully relocate 752 earthquakes with fine residual value 0 until 0.032 seconds. The trend of this earthquake sequence was spread but the main linearization is N 80 W, but it still makes a trend from a 48-degree dip angle. With the number of earthquakes in a narrow area and shallow depth within a short period of time, it should be suspected that there is a contact between faults and hot springs in the area so that these earthquakes can occur.