Scientists temporarily deploy instruments to collect ground-based magnetotelluric (MT) data

At each magnetotelluric (MT) site, three electrodes are installed. The electrodes require electrical contact with the ground and are buried in shallow holes about the width and depth of a spade head. The electrode is encapsulated in a canvas bag filled with bentonite, and water is poured in the electrode hole to improve the contact resistance. Electrodes are spaced about 50 m (164 ft) apart along NS and EW lines and are connected to the data logger at the center of the site. USGS photo by Andi Ellis.