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.     

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.     

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.     

Geological and macroseismic manifestations of the earthquake on October 16, 2011 in the Skovorodino region, Amur oblast

The epicentral zone and settlements that suffered from the M _S = 6.1 earthquake in the northwest Amur oblast are examined. Only secondary seismic dislocations were revealed and mapped in detail. The inspection of settlements and inhabitansts inquiry allowed estimation of the intensity of the macroseismic effect based on the MSK-64 scale. These forthwith primary factual data give an idea on the shaking intensity at the distant and nearest zones and precise location of the earthquake focus. The map of isoseists of the highest (7–8) intensity is drawn.     

Active Faults in the Kerch Peninsula: New Results

Doklady Earth Sciences - This paper reports recently obtained research data on active faults in the Kerch Peninsula. The compiled Map of Active Faults demonstrates foci of Late Holocene strong...     

Tectonic position and preliminary data on geological manifestations of the 2011–2012 Tyva earthquakes

The preliminary data on the tectonic position and seismological manifestations of the strong Tyva earthquakes that occurred on December 27, 2011 and February 26, 2012 are reported. The seismic ruptures are studied. The earthquake source structure in the earth’s depths is considered.     

Active tectonics of the area of the two Kaliningrad earthquakes on September 21, 2004

Resulting from the seismotectonic study of the Sambian Peninsula based on the interpretation of remote sensing data (satellite images and digital elevation maps), lineaments have been identified. They may be interpreted as active faults and flexure-fracture zones. These active faults, which are expressed in the form of gentle linear swells or steps in the relief, have been found and studied during the carried out field works. There are many discovered paleoseismic dislocations in the studied areas of active faults: fracture displacements, marks of liquefaction (sand dykes), near-fault folds. These seismic dislocations may indicate seismic shocks of 7–8 intensity points occurring in the neighborhood of a modern Kaliningrad city in recent geological history. The identified active structures (Yantarny Fault Zone and Bakalino flexure-fracture zone) could control sources of the 2004 Kaliningrad earthquakes.