Trevor Irons

Curie depth and inversion of aero-magnetic data with implications for Hazards on Pagan Island, Commonwealth of the Northern Mariana Islands

Airborne magnetic data have been used to aid in the hazard assessment on Pagan Island. Pagan Island is small active stratovolcano in the Commonwealth of Northern Mariana Islands approximately 320 km north of Saipan. The magnetic survey was part of a geophysical study that was carried out to evaluate the hazards of the Island in 2013. Pagan Island was evacuated during a major eruption in 1981. Recently the island has been assessed for a military training base, an area for mining pozzolan, and for rehabitation from the displaced population resulting from the 1981 eruption. With the remote location and rugged inaccessible nature of Pagan Island the airborne approach was the only logistically feasible way to provide a comprehensive assessment of the location of the heat sources within the volcano. Both spectral analysis and 3D inversion were used in order to provide two alternative means to determine depth to bottom of magnetic source. Locations of the heat sources within the volcano is one of critical pieces of information required for the government of the Commonwealth of the NorthernMariana Island to asses the safety an ultimately the use of the Pagan Island. Results were consistent between the two approaches and zones of shallow and deep Curie point isotherm were independently identified. The government has utilized these data after comparing with other passive seismic data to assist in the hazard assessment of Pagan Island.