Traces of Seismic Activity in Architectural Monuments in Derbent,Dagestan

Izvestiya, Atmospheric and Oceanic Physics - As a result of studies conducted in the city of Derbent, it is established that its monumental fortification structures erected at the end of the 560s...     

Neotectonics of the Kharaulakh sector of the Laptev Shelf

Seismotectonic deformation and crustal stress pattern have been studied comprehensively in major seismogenic structures of the Kharaulakh sector of the Verkhoyansk fold system and adjacent parts of the Chersky seismotectonic zone. The study focuses on neotectonic structures, deep structure, and systems of active faults, as well as tectonic stress fields inferred by tectonophysical analysis of Late Cenozoic faults and folds. The results, along with geological and geophysical data, reveal main strain directions and structural patterns of crustal stress and strain in the Arctic segment of the Eurasia-North America plate boundary. The area is a junction of mid-ocean and continental structures evolving in a mixed setting of extension, compression, and their various combinations. The rotation pole of the two plates is presumably located near Buor-Khaya Bay. In this case, extension is expected to act currently upon the neotectonic structures north of the bay and compression to control those in the south and southeast. This inference is consistent with the identified zoning of stress and strain in the Kharaulakh sector.     

Tectonic setting and geological manifestations of the 2003 Altai earthquake

Geological and geomorphic manifestations of the source of the earthquake that occurred in the southern Gorny Altai on September 27, 2003, are described. This earthquake, the strongest over the entire history of seismological observations, caused damage to buildings and structures in the Chuya and Kurai basins and was accompanied by exposure of its source at the surface with formation of a system of seismic ruptures trending in the northwestern direction. The linear zone of seismic rupture was traced for more than 70 km on the northern slopes of the North Chuya and South Chuya ranges, and a developed network of related splays was found. The secondary (gravitational and vibrational) seismic dislocations were expressed as downfalls, landslides, and gryphons in the pleistoseist zone. These dislocations occur over an area of approximately 90 × 25 km² that broadly coincides with the region of quakes having intensities of IX–VII. The paleoseismogeological investigations performed in the source region of the 2003 earthquake have shown that seven seismic events with M = 7.0–8.0 occurred in its source over the last 5000 years with a 500-to 900-year recurrence period. The study of the tectonic setting of the earthquake source in the Gorny Altai has allowed northward tracing of the main seismically active zones of the Mongolian and Gobi Altai, where earthquakes with a magnitude M > 7.0 occurred repeatedly, in particular, during the 20th century, and combination of all mountain systems of the Greater Altai into a common high-magnitude seismotectonic province.     

New findings on the sources of strong earthquakes in Kerch Peninsula based on paleoseismological data

This paper presents the results of the recent paleoseismological studies covering the entire Kerch Peninsula. The Yuzhnoberezhnaya fold-and-thrust belt extending along the southern coast of Crimea in the Black Sea was earlier considered the principal seismogenic structure. Our findings suggest that the seismic hazard on the Kerch Peninsula is largely related to potential strong onshore earthquake sources. The observed discrepancy between instrumental and paleoseismological data suggests that seismic quiescence exists in this region at present.     

A geological study of the epicentral area of the April 20(21), 2006 Olyutorskii earthquake

Primary and secondary earthquake effects were investigated (surface breakage and felt effects in the villages of Tilichiki, Korf, and Khailino) in the epicentral area of a large earthquake occurring in northern Kamchatka Krai. The primary effects include an extended surface break that can be followed for a length of about 140 km. The secondary (gravitational and vibrational) effects include soil slides and minor rockfalls, snow flows on slopes, resonant cracks, soil liquefaction phenomena consisting of mud cones, mud gryphons, and discharges of soil from cracks. Detailed maps showing the main types of earthquake surface effects have been made. Paleoseismic data show traces of several large earthquakes that have occurred in the Olyutorskii earthquake zone. Radio carbon dating of soil samples from these paleoseismic scarps revealed a history of great earthquakes occurring in Koryakia. In all, four seismic events with magnitudes about that of the 2006 Olyutorskii earthquake have occurred there during 8000 years, the return period of such events being 1000–2500 years.     

Geological and macroseismic effects of the Muya, 1957 earthquake and palaeoearthquakes in Baikal region

Intensity of the Muya, 1957 earthquake is assessed in localities based on macroseismic data and in epicentral area based on effects in natural environment; it is analyzed how these assessments correspond to each other and to instrumental location of epicenter, hypocentral depth, and magnitude; it is evaluated, how seismodislocations of the Muya earthquake could serve as control of palaeoseismostructure parameters in this region. Spatial distribution of macroseismic effect confirms relatively deep source (20–22 km). Deep source agrees with anomalously short surface rupture length (not more than 25 km); only a part of the source exposed on the surface. Comparison with length of palaeoseismostructures shows that it is a regional feature. Epicentral intensity based on surface ruptures is assed X degrees in ESI2007 scale. Ignoring geological effects will underestimate epicentral intensity up to two degrees. Source mechanism with three sub-sources is in agreement with segmentation of surface ruptures. Sub-sources are of strike-slip type with small normal component; essential normal slip at surface is probably not representative for the source and is due to accommodation of strike-slip movement along with a system of sub-parallel en echelon ruptures under tension.     

Detailed geological-geophysical studies of active fault zones and the seismic hazard in the south Yakutia region

Active faults play the key role in the formation of the morphological structures and control the seismicity in the Olekma-Stanovoi seismic zone. The detailed geological-structural and morphotectonic studies of fault zones made it possible to estimate the kinematics of the active faults and their activity degree in the Holocene (the last 10 000 years). The latter include old faults such as, for example, the Stanovoi Suture of the Proterozoic age. Most of these faults are the Late Mesozoic and Cenozoic in age. The studies were aimed at reconstructing the past seismogeological processes and were accompanied by trenching across morphological structures that are presumably associated with zones of active tectonic fractures preliminarily studied by geophysical methods. The applied approach allowed us to substantially specify the available information on the seismotectonics and the potential seismic hazard in the region.     

Origin of mass faulting during seismic activation in the Central Kuznetsk basin

In 2005, the low magnitude shallow hypocenter swarm seismic activation occurred in the central part of Kuznetsk Depression. It continues until today. The main objects of implemented field works were numerous ruptures appearing on the surface in the vicinity of the town of Polysayevo during the activation period. In addition to chaotically distributed subsidences, slumps, and cracks related to surface saggings above worked mine fields, linear fractures of the Earth’s surface were found. These fractures form regular structural parageneses and comprise a relatively large system of 7.6 km total length. Regular structural parageneses and displacements along the faults of up to 10 cm in amplitude allow us to consider them as surface tectonic fractures. The depth of earthquake hypocenters, based on instrumental data, reaches 5 km; i.e., quakes occur significantly deeper than mine fields, which are located down to a 500 m depth. It is possible to suppose that the summarized impulse effect of seismic activation had led to formation of seismotectonic deformations in the zone of an already existing fault. The difference of the described fractures from typically seismotectonic ruptures is their gradual, slow formation. Approximate time of the start of formation for the studied fractures is several years ago, with continuous renewal up to the present. Another difference of the surface fractures is their remote positions at the distance of 1–2 km west of the epicentral area of the earthquakes swarm.     

Recent Tectonic Rupturing on the Mud Volcano of Mount Karabetova,Taman Peninsula

Doklady Earth Sciences - In October 2019, extremely impressive, fresh ruptures of the surface on the mud volcano of Mount Karabetova were discovered. The ruptures are represented by all the main...