Geomagnetic Investigations in the Seismoactive Regions of Middle Asia

Abstract

Investigations of local geomagnetic field changes have been carried out in Middle Asia in the following regions: Tashkent, including Charvak reservoir, Fergana and Kyzyl-Kum. Since 1968, a variety of total field features have been observed there, including: (a) slow changes at separate stations, which may be explainable by compression or tension of individual earth’s crustal blocks; (b) a variety of field changes with amplitudes of a few gammas and periods of 0.5–2 years; (c) variations, which may be due to different conductivity of rocks; (d) anomalous changes in the fracture zones; (e) anomalous variations in the Charvak region, connected with reservoir filling. The amplitudes of these variations are 3–5 nT/year at Fergana, 8–9 nT/year at Kyzyl-Kum, 20–25 nT/year at Tashkent regions and up to 15–25 nT/year at Charvak reservoir area. Sometimes these anomalous changes are correlated with seismic activity (for example, Tashkent 1968 earthquakes).