I. Sokolova¹ , Y. Kopnichev²

¹Institute of Geophysical Research, Almaty, Kazakhstan
²Institute of the Physics of the Earth, Russian Academy of Science, Russian Federation

Abstract:

This study presents results from our investigation on the wave pattern of underground and atmospheric nuclear explosions conducted at the Lop Nor Test Site (China), and of tectonic earthquakes with epicenters close to the Lop Nor Test Site region. For our analysis, digitized analogue and digital seismograms from Central Asia seismic stations at distances of ~700–2000 km for the period of 1965-2016 were used. For seismic discrimination, the structure of short-period seismic fields from UNEs and earthquakes were studied. Threshold values for each parameter were determined, and the discrimination quality was estimated. To investigate geodynamic processes at the Test Site, the characteristics of short-period S-wave attenuation field in this area were considered using data from the Kazakhstan station BRVK. The methods were based on analysis of relative level of Sn and Pn waves (Sn/Pn parameter), and slope of P-coda envelopes. The UNE records show considerable diminishing Sn/Pn mean values and increasing slope of the P-coda envelopes from the end of 1960-s to 1990-s. The earthquake records from Lop Nor Test Site area showed a decrease of Sn/Pn values with time even after the UNEs series ceased. We conclude that the effects revealed were related to migration of deep-seated fluids as a result of long intensive induced influence.