Contacts

Address: 24a Marshal
Baghramyan Ave., 0019,
Yerevan, Republic of Armenia.
Tell: +374 10 526 517
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Email: georisk@sci.am

Publication

Major active faults of the collision area between the Arabian and the Eurasian plates. Continental Collision Zone Earthquakes and Seismic Hazard Reduction. IASPEI/IDNDR, Yerevan, (1994), 56-79

Abstract

Late Pleistocene and Holocene displacements on faults of the Eastern Mediterranean/ Turkey, Iraq and the adjacent part of Iran, the Caucasus republics and the adjacent part of Russia have been studied. They show that northern drift of the Arabian plate transforms (because of resistance of the Black sea cold microplate) into: (1) the western drift of Anatolia along the North Anatolian fault zone/ and (2) the northern drift and compression of the Lesser Caucasus, which is manifested by strike-slip and reverse motion on the North Armenian active fault arc. The drift of the Lesser Caucasus results in its thrusting over the Rioni and the Kura basins, and underthrusting together with both basins under the Great Caucasus, the latter experiencing transverse shortening and uplifting. The Great Caucasus striking NW bears significant component of right lateral shearing along it.

Screening piezometric levels prior to analysis of groundwater behaviour during seismic crises: example in the Lesser Caucasus. Journal of Hydrology, France, (1995) 40(5), 647-662

Abstract

Seismic crises can induce more or less drastic and long duration modifications of water table piezometry, especially in confined media. Piezometric observations made in boreholes deliver basic signals, which can be disturbed by the atmospheric pressure and earth tides. One method of processing the raw piezometric signals is proposed (FIPAC computer program). Two examples of its application are analysed from results registered in the Lesser Caucasus range (hourly measurements during several years) related to three historical major earthquakes (Spitak, Armenia in 1988; Racha, 1991 and Barysakho, 1992, in Georgia).

Relationships between seismic activity and piezometric level changes in the Arax basin (SW Armenia): attempt at a typology of seismically induced piezometric anomalies. Tectonophysics. (1997) 273, 293-316.

Abstract

We analyze the relationships between seismicity in the Arax basin, and the water level changes of two deep confined fresh water reservoirs, monitored by two wells with hourly records of piezometric levels. The reservoirs are alimented by the northern faulted border of the basin and discharge on the southern border. In the vicinity of the recording wells, the water flow may be considered as stationary on a time scale of months.

Tectonic and neotectonic studies indicate that the basin is located in an area where the state of stress varies, with the minimum stress (s 3) oriented horizontally and E-W to NE-SW and the maximum stress (s 1) varying from vertical to horizontal.

Analysis and filtering of hydrographs yields cleaned curves where seismically induced piezometric level changes can be identified. The most relevant observations are the following:

Each well records events occurring only in the tectonic block where it is located, independently of earthquake magnitude.

Ten types of seismically induced piezometric anomalies are identified, each of them resulting from a peculiar reaction of the reservoir to a local change of the strain state induced by the earthquake. The duration of the deformation may either be short (about 1 week) or long (about 2 months).

Level changes of the aquifer often postdate earthquakes and are not precursors.

We attempt to correlate the state of stress and the anomalous behavior of the piezometric levels in the two wells. In the northern reservoir, s 3 is perpendicular to the flow lines, the hydraulic gradient is lower than in the south, the rocks are fractured and the permeability is mainly of a fracture type. Seismic energy and water level changes are well correlated. In the southern reservoir, s 3 and the flow lines are parallel and the water-bearing rocks consist in a continuous medium where the permeability is mainly of a pore type. There is a poor correlation between seismic energy and water level changes.

Relationship of Late Quaternary tectonics and volcanism in the Khanarassar active fault zone, the Armenian Upland. Terra Nova. (1997) 9, 131-134.

Abstract

The Syunik rhombus-like structure in the Khanarassar active dextral fault zone of Armenia is a typical pull-apart basin, formed between terminal parts of two adjacent en echelon fault segments. Some component of subsidence associated with the faults of the structure is found between the en echelon segments; nevertheless, the dextral component continues to be predominant even on the boundaries of the pull-apart basin. The late Pleistocene and Holocene lava volcanoes of the basin are also associated with those faults that have a component of extension. The relative ages of fault displacements and volcanic eruptions have been identified by the mutual correlation of lavas, moraines and topographic features and by archaeological and radiocarbon dating. According to the interpretation of rupturing and volcanism, major earthquakes and volcanic eruptions appear inter-related and three pulses of such activity during the earlier and middle Holocene have been identified.

Recent geodynamic characteristics in the Arabian-Eurasian and Indian-Eurasian collision region by active fault data. Tectonophysics (1999) 308, 1-2

Abstract

WA part of the Alpine-Himalayaii orogenic belt is studied, limited by 30-104°E and by 26-46°N to the west of 64°E and 26-56°N to the east of 64°E. A technique is proposed to calculate the field of the recent (Late Pleistocene and Holocene) deformation rate tensors in the upper crust (15 to 20 km) by active fault data. A hydrodynamic model of the medium is used for the calculation. Monotonous fault segments as long as 10-15 km are taken as the elementary cells of the medium. The cell square (the length multiplied by the depth) multiplied by the displacement vector magnitude, gives the geometric moment. Similar components of the local tensors of the geometric moments are summarized within the windows into which the region is divided. Finally, parameters of the axes of principal rates of deformation are calculated, and their directions and magnitudes are mapped. This tectonic deformation is compared with the seismotectonic one calculated by focal mechanisms of earthquakes. The compiled maps show: a concentration of high deformation rates in the plate boundary zones (especially in front of the southern plate syntaxes) and a smaller concentration in some microplate boundary zones; a predominance of the N-S-trending shortening and of strike-slip type of deformation. The rates of shortening and lengthening are usually almost equal to each other and differ essentially (the shortening rate is higher than the lengthening) only in specific sites. These are areas of intense recent detachment or late Quaternary volcanism. It seems that the double-axis lengthening (extension) is suitable for these processes. © 1999 Elsevier Science B.V. All rights reserved.

Hydraulic behaviour of one largest artesian basin (Lake Sevan) crossed by a pluri-kilometric active fault (Armenia). Press Univ. of Grenobl, France, (2000), 181

Abstract

The analysis of three hydrogeological test sub-basins composing the Sevan artesian basin leads to the following conclusions:

hydraulic independence of surface and ground confined waters of the basin;

weak barometric (3-6cm) and tidal (0.02-0.025 bar at self-outpouring wells) influence on the confined aquifers;

fundamental importance of the snow cover in the feed of aquifers with considerable time dephasing;

reconstruction of " precipitation-piezometry " relationship by means of two models :

a. Mathematical Model of Relationship Between Precipitation and Piezometry ;

b. Statistical Model of Relationship Between Precipitation and Piezometry;

identification of piezometric anomalies related solely to local seismic activity (within the pull-apart tectonic basin of Sevan);

prospect of the artificial increase of the lake water level, which has dropped for 17 meters during the two-thirds of the century as a result of over-exploitation, requires clarification as to the required height to which the water table shall be increased, water sources to be used for that purpose and the time required to effect such increase of the water table level in the lake.

Tectonic impact on the Lake Sevan environment (Armenia). Environmental Geology. (January 2001) 40 (3) • © Springer-Verlag 279-288.

Abstract

The geology of Lake Sevan is characterized by the structure of a pull-apart basin. Methane emission from the lake surface correlates with evidence of physical and chemical water properties, remote sensing, etc., and suggests its possible emission from active fault zones at the lake bottom, as well as emission of biogenic methane from the fermentation of bottom organic remains. Correlation with anomalies in the lake bottom geochemistry suggests a high permeability of active fault zones and suggests that geodynamic, seismic and geo-chemical activity across the fault zones during the buildup to the M=7.1 Spitak earthquake led to plankton depression, which resulted in a large number of fish dying in 1984, and ended with a seismic disaster in 1988.

Environmental Geology. (January 2001) 40 (3) • © Springer-Verlag 279-288.

Estimation of the slip rates and the recurrence intervals of strong earthquakes on the fault system of Pambak-Sevan-Sunik (Armenia): segmentation and relation with volcanic activity. (2001), PhD Thesis, Montpellier II University, France, 246

Abstract

The report is dedicated to the study of active faults in Armenia. A detailed study was realised on the most important active fault of Armenia: Pambak-Sevan-Sunik (FPSS) fault. The first part of the report present the FPSS in the context of the continental collision between the Eurasian and Arabian plates. The following part considers the active tectonics and seismicity in detail at the scale of Armenia.

The main part corresponds to a detailed study of the FPSS to clarify the trace and kinematics of the fault and define its segmentation. A paleoseismologic and archeoseismologic study was realised on several sites along the fault, which allowed revealing evidence about several important earthquakes of the past, definition of rupture extensions, evaluation of slips and therefore, estimation of magnitudes of these events. These data also allowed estimations of slip rate and recurrence intervals for strong earthquakes on the FPSS. Based on these constituents of seismic hazard, a first estimation of the seismic risk associated with this fault is proposed.

PhD Thesis, Montpellier II University, France, (2001) 246.

 

The large earthquake of Garni (Armenia), 14 June 1679.

The large earthquake of Garni (Armenia), 14 June 1679: a historical revision. Journal of Seismology, (2002), (submitted for publication)