Very long period Magnetic and Electric Field Observatories in China: Imaging Mantle Transition Zone Conductivity

Abstract:

In a companion paper (Wang and Egbert, 2020) we describe the estimation of very long period (250s~ 4 days) MT quasi-impedance from 10 years Magnetic and Electric Field Observatories in China. Here we study the Earth’s mantle conductivity. More electric (from 2000~) and magnetic (from 1950) data have been collected to estimate MT impedance using ELICIT (Joan et.al, 2014) and C-response. We estimate the static shift of the MT impedance by comparing the long-period MT results to equivalent MT impedances from C-response. Combining the equivalent MT impedances and undistorted MT impedances we obtain in distortion free impedance estimates for periods 1000s < T < 20 days. 1D Occam inversion was used to image the mantle conductivity and resulted in high conductivity in the mantle transition zone of east China due to water carried deep into the Earth by the subducting old, and cold, Pacific Plate.