Crustal structure of the North Anatolian and East Anatolian Fault Systems from magnetotelluric data

• Resistivity structure of East Anatolian and North Anatolian Faults studied with MT.
• East Anatolian Fault characterized by conductor extending through crust.
• North Anatolian Fault characterized by more modest conductor.
• Resistivity structure may be linked to maturity of the fault zone.

Magnetotelluric (MT) studies can map subsurface resistivity structure and have located zones of low resistivity (high conductivity) within major strike-slip fault zones worldwide which have been interpreted as regions of elevated fluid content. This study describes MT data from the eastern part of the North Anatolian and the East Anatolian Fault Systems (NAFS and EAFS) and presents the results of the first MT studies of these faults. The inversion of the MT data produced 2-D resistivity models which showed that both fault systems are underlain by a broad low resistivity zone that extended into the lower crust. However, the resistivity beneath the East Anatolian Fault System was much lower than beneath the eastern part of the North Anatolian Fault System. These conductors begin at a depth of 10 km – not at the surface as on the central San Andreas Fault (SAFS). This difference is interpreted as being due to the fact that the EAFS and NAFS are young fault systems characterized in the upper crust by multiple fault traces – as opposed to the SAFS that has evolved into a single through going fault. Different stages of the seismic cycle may also influence the resistivity structure, although this is difficult to constrain without knowledge of time variations in resistivity structure at each location.