» Gedung UPT Perpustakaan
Rahat volcanic field is one of the basaltic fields in Saudi Arabia that has threemajor geohazard events; the historical eruption (1256 CE), the fissure eruption (~4500–1500 BP), and seismic swarm (1999). These events were studied and evaluated using geophysical and geochemical studies as well as volcanological studies. Geophysical studies include gravity, seismic, and magnetotelluric surveys. In the current research, the magnetotelluric data will be analyzed using 3D inversion technique in order to image the subsurface resistivity setting of the study area. Results from3D inversion of theMT data revealed fourmajor resistivity structures. The first is a layer of intermediate resistivity (40–250?-meters)which is thicker (~800m) to the south-west and thinner to the eastern edge, mostly covered by exposed Precambrian basement. This layer is underlain by resistive (N1000?-metres) granitic basement. Intruding into the resistive basement are two near-vertical conductive (b20?-metres) structures.One is located immediately west of the historic eruption (1256 CE) centre in the north, at a depth of about 15 km. The other intrusive is on the southern end of the survey area, also at a depth of about 15 km. Two conductive “channels” trending NW-SE and NE-SWwere observed at depths of about 18 km. The NE-SWaligned “channel” runs through the northern intrusivewhile theNW-SE trending “channel” runs in themiddle of the study area and connects both intrusive. The conductive intrusive and “channels” may be attribute partial melts stored in the preexisting structures within the lower crust. Although the youngest known trachytic eruptions from the study area are several hundred thousand years old, recent and ongoing seismicity strongly suggest there may bemagmatic activities in the lower and probably upper crust.