Survey and observation of earthquake swarm and buried geothermal resources by seismological analyses, seismic tomography, magnetotelluric, and gravity modeling of the upper crustal structure of the Yalova-Termal Region

• Subsurface imaging with high resolution traveltime seismic tomography • Subsurface geothermal source delineation with 3D magnetotelluric inversion • Integrated geophysical application of seismic tomography, magnetotelluric, and gravity in a seismically active area with relation geothermal sources This study presents the results of various geophysical methods applied in and around a thermal source in Yalova, Türkiye. Termal town, located on the seismically active Armutlu Peninsula, is the focus of the investigation. The research explores earthquake swarms and their relationship with hydrothermal activity in the area. The findings are compared using seismological analyses and different geophysical techniques, including seismic tomography, magnetotelluric (MT), and gravity surveys. A previously unrecognized boundary of the geothermal source was identified using 3D resistivity models derived from MT data, corroborated by the location of an existing well. Key observations include a high density of earthquake events, sharp variations in seismic tomography parameters (Vp, Vs, and Vp/Vs ratio) particularly along fault zones, as well as high-resistivity and negative Bouguer gravity anomalies in and around Termal town. Despite differences in resolution among the three geophysical methods, their results were consistent and complementary. The MT and gravity data show comparable features down to approximately 1 km depth. While exact comparisons at shallow depths are limited, the anomalies identified in the seismic tomography appear to extend from those observed in the MT and gravity datasets.