On tectonophysical interpretation of recent vertical crustal movements

Abstract

Recent crustal movements are components and the direct continuation of some neotectonic movements i.e. the Neogene-Quaternary stage of the earth's development. According to geodetic and oceanographic data these crustal movements are constantly taking place everywhere on the continents and probably on the ocean floor. Their velocity and velocity gradients are certainly different on platforms from that in orogenic regions. Orogenic regions are characterized by higher velocity, varying from several mm to several cm per year, and to an even greater degree by the different character of the movement. The velocity gradient in these regions reaches values of 10 −6–10 −5/year. A peculiar indication of recent movements is their irregularity in time. Periodic movements are typical for platforms; orogenic regions are characterized by sharp increases in velocity by 1–2 orders of magnitude and their gradients by 2–3 orders, close to the time occurrence of earthquakes. The deep processes generating the measured recent crustal movements are manifested also in earthquakes, the state of stress of rocks and anomalies of gravitational and other fields. Thus estimations of recent tectonic activity should be based on the whole complex of quantitative data, such as the velocity and velocity gradients of recent movements, values of stress in mines, and seismicity. To study the deep processes causing the present tectonic activity, it is necessary to determine the types of crustal deformation occurring in different geotectonic regions. The relationships between recent movements and the distribution of earthquakes in the regions with a high degree of crustal activity allow to identify four types of movement: pleistoseismic, hyposeismic, kryptoseismic and teleseismic.