Post-seismic relaxation from geodetic and seismic data

We have examined the aftershock sequence and the post-seismic deformation process of the Parkfield earthquake (2004, M = 6, California, USA) source area using GPS data. This event was chosen because of the possibility of joint analysis of data from the rather dense local GPS network (from SOPAC Internet archive) and of the availability of the rather detailed aftershock sequence data (http://www.ncedc.org/ncedc/catalog-search.html). The relaxation process of post-seismic deformation prolongs about the same 400 days as the seismic aftershock process does. Thus, the aftershock process and the relaxation process in deformation could be the different sides of the same process. It should be noted that the ratio of the released seismic energy and of the GPS obtained deformation is quite different for the main shock and for the aftershock stage. The ratio of the released seismic energy to the deformation value decreases essentially for the post-shock process. The similar change in the seismic energy/deformation value ratio is valid in a few other strong earthquakes. Thus, this decrease seems typical of aftershock sequences testifying for decrease of ratio of elastic to inelastic deformation in the process of post-shock relaxation when the source area appears to be mostly fractured after the main shock occurs, but the healing process had no yet sufficient time to develop. © 2017 Institute of Seismology, China Earthquake Administratio

Post-seismic relaxation from geodetic and seismic data

We have examined the aftershock sequence and the post-seismic deformation process of the Parkfield earthquake (2004, M = 6, California, USA) source area using GPS data. This event was chosen because of the possibility of joint analysis of data from the rather dense local GPS network (from SOPAC Internet archive) and of the availability of the rather detailed aftershock sequence data (http://www.ncedc.org/ncedc/catalog-search.html). The relaxation process of post-seismic deformation prolongs about the same 400 days as the seismic aftershock process does. Thus, the aftershock process and the relaxation process in deformation could be the different sides of the same process. It should be noted that the ratio of the released seismic energy and of the GPS obtained deformation is quite different for the main shock and for the aftershock stage. The ratio of the released seismic energy to the deformation value decreases essentially for the post-shock process. The similar change in the seismic energy/deformation value ratio is valid in a few other strong earthquakes. Thus, this decrease seems typical of aftershock sequences testifying for decrease of ratio of elastic to inelastic deformation in the process of post-shock relaxation when the source area appears to be mostly fractured after the main shock occurs, but the healing process had no yet sufficient time to develop. © 2017 Institute of Seismology, China Earthquake Administratio

Earth’s Surface Deformation on Mount Etna: GPS Measurements, Interpretation, Relationship to the Mode of Volcanism

Abstract: We present results from a study of lateral Earth's surface deformation and vertical movements in the area of the Mount Etna active volcano (Sicily, Italy) based on observations by global satellite navigation systems in 2011–2017 at time intervals of 24 hours at sparse stations of the regional geodetic network. The study of Mount Etna is especially important because (1) the volcano stands in a densely populated area, (2) the eruptions are nearly continuous, and (3) the location of the volcano is inconsistent with plate tectonic concepts. Subregional trends have been identified in the deformation of the area of study. Extension was recorded, not only around the summit crater, but also far from it, in the Ionian Sea. This circumstance suggests the existence of an extensive plumbing system at depth whose sources are far from the active summit crater. We discuss geological and geophysical survey results of the coastal area and the sea area in the region. It is shown that Earth’s surface deformation can be suitable studied from observation points of the existing networks that are rather distanced from each other, but cover a large area. © 2019, Pleiades Publishing, Ltd

Statistical Analysis of Natural Disasters and Related Losses

XI, 81 p. 84 illus.online resource

The active tectonics of the Vuoksi Fault Zone in the Karelian Isthmus: parameters of paleoearthquakes estimated from bedrock and softsediment deformation features

The area under study is located in the south-eastern periphery of the Fennoscandian crystalline shield. At present this is a tectonically quiet region without large seismic events. But it is well known that in post-glacial time the Fennoscandian shield was an arena of active postglacial tectonics and large earthquakes. The evidence for such events was found in various parts of Fennoscandia. The traces left by some paleoearthquakes show an undisputed character of large post-glacial faults some tens of kilometres long and of a few meters in displacement. However, some other features left by earthquakes are under discussion. Numerous deformations in bedrock and in soft sediments which can be considered as being due to earthquakes were found in the Russian Karelia. Interpretation of some of these deformation structures can lead to different conclusions about their origin, for example, weathering, cryogenic, glacial, and gravitational factors. One possible way to overcome these difficulties is an integrated study of different types of deformations at key sites, comparison of these with each other and with the tectonic features of the region, and the search for common structural and kinematic features. Another problem is the estimation of parameters of paleoearthquakes. This problem includes the determinations of their location, intensities, magnitudes, and age. The key site under study is located in the northern part of the Karelian Isthmus in the re-activated (during post-glacial time) tectonic zone (the Vuoksi Fault Zone), whose signature in the relief is seen in the form of the straight-line valley of the Vuoksi River. We studied different types of post-glacial seismogenic deformations at this locality. There are seismically induced gravitational and vibrational deformations in solid rock, as well as folds and ruptures in loose sediments. The key site of large deformation examined here includes three zones: 1) the main zone of deformations or the Central Fractured Massif (CFM); 2) the seismically induced colluvial zone; 3) the outer zone of deformations in loose sediments. We have established that all types of deformations are kinematically similar in the CFM and around it (at distances of a few kilometres). A detailed examination of deformations and their spatial and temporal relationships allows us to distinguish three generations of earthquake-induced deformations: 1) Late Glacial, 2) Early Holocene, and 3) Middle to Late Holocene. We estimate the intensities of the respective earthquakes as I=IX, IX, and VII-VIII. Clearly, the intensities decrease from post-glacial to present time, but the recent level of seismicity is unclear and may be much higher than hypothesized. In addition, the evidence for shear kinematics of the fault shows that earthquakes were not only caused by post-glacial rebound, but also resulted from a different tectonic mechanism possibly related to plate tectonics

On the estimation of stationary level of earthquake catalogs

Abstract: In this paper we analyzed the stationary level of JMA catalog of magnitude and time intervals between events. It was shown, that these distributions are non-stationary and the time dependence of Gutenberg – Richter law parameter could be represented as a superposition of two quasi-periodical dynamical systems with short and long periods.Note: Research direction:Mathematical modelling in actual problems of science and technic