SEISMIC IMPACT ESTIMATION FROM DATA ON DEFORMATIONS AND DISPLACEMENTS IN ROCK MASSIFS

• Main Authors: Mikhail V. Rodkin, Аndrei A. Nikonov, Sergei V. Shvarev
• Format: Article
• Language: English
• Published: Institute of the Earth's crust, Siberian Branch of RAS 2015-09-01
• Series: Geodinamika i Tektonofizika
• Subjects: quantification of seismic impacts on rocks; major paleoearthquakes in fennoscandia; impacts of earthquakes and explosions on crystalline rocks
• Online Access: https://www.gt-crust.ru/jour/article/view/163

Local rock dislocations and shifts, which occur due to strong seismic impacts, are studied. Natural cases under review include displacements that occurred after strong earthquakes in the 20th century and paleoseismic dislocations revealed by the authors in the crustal rocks in the south-eastern (Russian) part of the Fennoscandia shield. The major goal of the study was to determine parameters of the paleoseismic events in terms of intensity, I, and magnitude, M. Two independent options were used: (1) estimation with reference to similar cases in the instrumental measurements period and to the currently applied scaling systems, and (2) introduction of physical characteristics of disturbances of particular types and habitus and fixed values of displacements of the rock blocks. Numerous local disturbances of the rock massifs with significant rock shifts were systematically reviewed as a set of standard models. Values of mass velocities of seismic impacts (peak ground velocities, PGV), which were needed for initiation of the revealed dislocations, were estimated. In many cases, PGV values were above 1 m/sec, i.e. considerably higher than values conventionally accepted (for ground conditions). For clarifications, data on strong movements and explosions were used, and the whole set of data was found reasonably consistent. It was concluded that the cases with PGV>1 m/sec corresponded to focal areas of earthquakes with M>6 (mainly in the deglaciation period). A graphical chart is proposed for estimation of magnitudes and hypocentral distances of initiating earthquakes in case of maximum PGV within a range from 0.01 to 5.00 m/sec. Based on the graphical chart, parameters are estimated for earthquakes that might have caused the dislocations observed on the main sites of the region under study.