Palaeoseismicity of the Dinar fault, SW Turkey

The NW–SE-trending Dinar fault is an active normal fault upon which the 1 October 1995 earthquake ( M  = 6.1) occurred. The 1995 earthquake resulted in a c. 10-km-long surface rupture with the south side down-thrown by 50 cm. Investigations of two trench sites perpendicular to the 1995 rupture suggest at least two prior large earthquakes in historical times. Radiocarbon dates and historical records constrain the age of events between 1500 bc and ad 53, event 2 possibly coinciding with the earthquake that damaged Dinar (the ancient city of Apamea Kibotos) in c. 80 bc and event 1 around 1500 bc. Surface displacements determined for events 1 and 2, compared to the 1995 surface faulting, indicate that M > 6.8 earthquakes were associated with each rupture. Using the total displacement in trenches, a slip rate of about 1 mm yr⁻¹ can be estimated for the Dinar fault. Observations suggest that the return period for large earthquakes in the Dinar area is about 1500–2000 years.     

23 October 2011 Van (Turkey) earthquake

An earthquake of Mw7.2 on 23 October 2011 occurred in the Van region of Eastern Turkey. The main shock and long series aftershocks caused significant damage and claimed 644 lives. The particular features and the lessons learned are covered.     

Geological and archaeological evidence for post-Roman earthquake surface faulting at Cibyra,SW Turkey

The NE–SW-trending Burdur–Fethiye fault zone is one of the major active fault zones of southwestern Turkey and the ancient city of Cibyra is located on this zone. Segments of the Burdur–Fethiye fault zone have ruptured in the historical period and during the 20th century. A detailed investigation in the ancient city of Cibyra showed the presence of faults sinistrally offset sitting rows of the stadium up to 50 cm. In addition, there are broken corners of blocks, collapsed walls, broken columns, and tilted and toppled blocks in existing major buildings in the city centre. Field observations showed that fractures and associated damage at Cibyra were produced by a post-Roman earthquake, possibly during the 417-A.D.-earthquake which had an intensity of 9 on the MSK scale.     

Evaluation of liquefaction in Karasu River floodplain after the October 23, 2011, Van (Turkey) earthquake

Natural Hazards - The eastern shore of Lake Van was shaken by a powerful earthquake (M w 7.2) on October 23, 2011. The epicenter of the earthquake was located at about 30 km north of the...     

The van earthquake on October 23, 2011: Natural and technogenic causes

A measurable effect of mass bombing on weak to moderate seismicity, endogenous microseism intensity, and acceleration of tectonic processes has been found. This effect is seen in the regime of strong and catastrophic earthquakes, a decrease in magnitude and time for their preparation, and lesser seismic hazard. The M = 7.8 Van Earthquake on October 23, 2011, was induced to occur early due to mass bombing in Libya and other regions of North Africa; however, the induced character caused its magnitude to be less by several tenths than it might have been.     

The earthquake of September 6, 1975 in Lice (eastern Turkey)

The mechanism of faulting for the Lice earthquake of September 6, 1975 is thrust fault, the compressional axis is horizontal and perpendicular to the Taurus mountains with 180° azimuth and 2° plunge. This corresponds to northward movement of Arabia. The T-axis is nearly vertical. The slip vector has 15° azimuth and 65° slip angle for the fault plane which is simistral and has N72°E azimuth and dips 45° NW. The intensity distribution pattern, the location of the main aftershock epicentres, the geological aspect of the region, and the limiting boundaries of different zones indicate the predominence of the east—west direction and are in good agreement with our focal-mechanism solution.     

The Uttarkashi earthquake of 20 October 1991: field observations

The epicentre of the destructive 20 October 1991 earthquake is in the north-east of the Uttarkashi region of the Higher Himalaya. The earthquake was felt up to 250–350 km away from Poh and Keylong in the north to Delhi in the south and beyond Chandigarh in the west. Seismologists of the Seismotectonic Group of Wadia Institute of Himalayan Geology studied fissures, surface breaks, and the foreshock and aftershock activity caused by this event. Land fissures show normal dislocations of 0.06–1 m, run E-W and NE-SW in the epicentral region and could be followed for 30–40 km.     

The Erzincan earthquake of 13 March 1992 in Eastern Turkey

The 13 March 1992 Erzincan earthquake, M=6.8, occurred in the eastern half of the Erzincan basin. The largest aftershock took place near Pülümür on 15 March 1992. No clear surface breaks were observed, although teleseismic studies suggested that it was a strike-slip earthquake striking parallel to the North Anatolian fault, with a focus of approximately 10±2 km depth, 30 km rupture length, 95 cm of slip, and a 1.16×10²⁶ dyn.cm seismic moment. The aftershock distribution concentrated at an area of the intersection between the North Anatolian fault and the Ovacik fault. These results indicate that the previously suggested seismic gap along the North Anatolian fault, east of Erzincan, still remains unruptured.     

Hummocky moraines in the Namaras and Susam Valleys,Central Taurids,SW Turkey

Late Quaternary glacial features have been found in the Central Taurid Mountains, in U-shaped valleys located at an altitude of more than 2000 m and surrounded by mountain ranges reaching 2850 m. No present day active glaciers exist in this area where the snowline elevation lies at about 3500 m. The Namaras Valley and its tributary Susam Valley are characterized by coarse loose material forming chaotic knob-and-kettle topography. Mounds, 1–10 m high and 10–30 m wide, are separated by 5–30 m wide, several meters deep, irregular depressions. The upper surfaces of the mounds are covered by angular to subangular limestone pebbles and blocks and internal sediments show a typical diamicton appearance with pebbles suspended in a muddy to sandy matrix. These chaotic structures are interpreted as hummocky disintegration moraines from former active glaciers. Successive cross-valley morainic ridges, up to 200 m high and several hundreds of meters long, limit the down-valley extension of these hummocks, and are interpreted as ice-marginal moraines. In the tributary Susam Valley, part of the coarse loose material forms a 200–250 m long and 90–120 m wide tongue-shaped structure with successive arcuate ridges and furrows at its down-valley reach. This structure, which is connected upward to a talus slope and perched cirque, ressembles the morphology of a periglacial rockglacier but is interpreted as the disintegration moraine controlled by small periodic retreat and readvance of the last active ice-front in this region.     

Seismotectonic significance of the 29 January 1989 Etne earthquake, SW Norway

The integrated analysis of geological, seismological and field observations with lineament data derived from satellite images allows the identification of a possible seismogenic fault zone for an earthquake which occurred near Etne in southwestern Norway, on 29 February 1989. The hypocentre of the earthquake was located at the mid-crust at a depth of 13.8±0.9 km which is typical of small intraplate earthquakes. The Etne earthquake occurred as a result of normal faulting with a dextral strike-slip component on a NW–SE trending fault. Available geological and lineament data indicate correlation of the inferred seismogenic fault with the NW–SE trending Etne fault zone. An aeromagnetic anomaly related to the Etne fault zone forms a regional feature intersecting both Precambrian basement and allochthonous Caledonian rocks. Based on these associations the occurrence of the Etne event is ascribed to the reactivation of a zone of weakness along the Etne fault zone. Slope-instabilities developed in the superficial deposits during the Etne event demonstrate the existence of potentially hazardous secondary-effects of such earthquakes even in low seismicity areas such as southwestern Norway.     

Prediction of the 6.6 Grevena-Kozani earthquake of May 13, 1995

Seismic Electric Signals (SES) were recorded by VAN-group on April 18–19, 1995, at Ioannina station; they resulted in an official prediction that was sent (two weeks before the earthquake occurrence) to the Greek authorities as well as to various International Institutes.The observation of these electrical variations was confirmed by Gruszow et al. (1996); however, they claim that these signals could be attributed to a (non determined) nearby artificial source with huge intensity (IL≈4 × 10⁴Am, for r ≈ 2 km. or 1.6 × 10⁵Am, for r ≈ 4 km). This claim is not valid, because, such an artificial source (cf. horizontal point current dipole) should have produced: (a) electrical field variations having amplitudes two orders of magnitude, larger than the observed ones; this is theoretically shown and experimentally verified and (b) magnetic field variations mainly on the horizontal field, while, in the present case, they have been recorded mainly on the vertical component.Furthermore, we show that the above SES obey the criteria, suggested by Varotsos and Lazaridou (1991), for discriminating SES from noise.     

Pushover and nonlinear time history analysis evaluation of a RC building collapsed during the Van (Turkey) earthquake on October 23, 2011

The nonlinear seismic behavior of a collapsed reinforced concrete (RC) residential building in the city of Van in Turkey is investigated by the static pushover and nonlinear time history analyses. The selected RC structure was designed according to the 1975 version of Turkish Earthquake Code (TEC-1975). The building had experienced heavy damage, and it was demolished in the Van earthquake on October 23, 2011. The 2007 version of Turkish Earthquake Code (TEC-2007) is considered for the assessing seismic performance evaluation of the selected RC building. The RC structure presents collapse performance level under the earthquake loads. Besides, the analytical solutions show that different performance levels for the sections are obtained from the pushover and nonlinear time history methods.     

The October 20, 2011 Mw 5.1 Talala earthquake in the stable continental region of India

The Talala (Sasangir) area in the Saurashtra region of Gujarat, western India, is experiencing tremors since 2001. The swarm type of earthquake activity in 2001, 2004, and every year from 2007 onward has occurred after the monsoon and lasted 2?C3?months each time. In 2007 some 200 shocks (largest M_w 5.0) and in 2011 about 400 shocks down to M1 are well recorded with 1?C2?km location error. The focal depths are about 2?C10?km and shocks are accompanied by blast-like subterranean sounds. The epicenter (21.09?N 70.45E, focal depth: 5?km from location program, 3?km from MTS) of the October 20, 2011 mainshock occurred about 12-km WNW of Talala town or 8-km SSW of the 2007?M _w 5.0 earthquake epicenter. The epicentral trends deciphered from local earthquake data indicate two ENE trends (Narmada trend) for about 50?km length and a conjugate 15-km-long NNW trend (Aravali trend). The focal mechanisms by moment-tensor analysis of full wave forms of two 2007 events of M_w 4.8 and 5.0 and the 2011 event of M_w 5.1 indicate rupture along either of the two trends. The ENE trends follow a gravity low between the gravity highs of Girnar mounts. Seismic reflections also indicate a fault in the area named Girnar Fault. Most of Saurashtra region including the Talala area is covered by Deccan Trap Basalt forming plateaus and conical ridges. There is no major fault within Saurashtra Peninsula though it is believed to have major faults along the boundaries that are non-seismic. The intensity of the October 20, 2011 Talala earthquake is estimated to be 6.5 in MM scale while isoseismals of 6, 5, and 4 and felt distance give M_w 5.1 based on Johnston??s 1994 empirical regressions. The source parameters of the 2011 Talala earthquake are estimated using data from 14 broadband seismograph stations. Estimated seismic moment, moment magnitude, stress drop, corner frequency, and source radius are found to be 10^16.6 N-m, 5.1, 1.6?MPa, 1.3?Hz, and 2,300?m, respectively. The b and p values are obtained to be low, being 0.67 and 0.71, respectively. PGA of 35?cm/sec² is noted and the decay rate of acceleration has been estimated from strong motion data recorded at 5 stations with epicentral distances ranging from 32 to 200?km.     

Hydrogeochemical evaluation of Umut geothermal field (SW Turkey)

Tekkehamam geothermal field is located in the South of Menderes Graben (Aegean region) and is one of the most important geothermal sites of Western Anatolia. Umut geothermal field is a part of the Tekkehamam field. This study was conducted in order to determine the origin and hydrogeochemical properties of the geothermal waters. For this purpose, sampling was done in order to check the chemistry of the water, and ¹⁸O, ²H isotope analyses done at four wells, nine natural springs and three cold water sources. According to the results of the chemical analysis, the geothermal waters were determined to be of Na + K-SO₄ type. Additionally, ¹⁴C and ³H analyses were done in selected well and spring waters for the purpose of age determination of groundwater; most of the waters were determined to be submodern. Geothermometer calculations show that the reservoir temperature for the Umut geothermal field ranges between 148 and 180 °C. Stable isotope results indicate that Umut geothermal waters are meteoric in origin. Mixing between shallow and deep waters is the dominant subsurface process that determines the physical and chemical character of the waters.     

Material properties of the Menderes Massif Marbles from SW Turkey

Marbles are extensively quarried at four different stratigraphical levels from Permo-Carbonifereous to Paleogene in the southern flank of the Menderes Massif in SW Turkey. These marbles differ in color, texture and pattern depending on their stratigraphical levels and are well known in the international trade as the Mugla Black (Permo-Carbonifereous), Mugla White (Cretaceous), Milas Lemon, Lilac, Aubergine, Pearl, Veined and White (Triassic) and Aegean Bordeaux (Paleogene) marbles. The mineralogical, chemical, physical and mechanical properties of the representative marbles samples obtained from the quarries working in four major metamorphic carbonate horizons in the cover successions of the Menderes Massif's southern flank in SW Turkey are determined and the results of over 1700 tests carried out on the selected marble samples are presented. The mean test values of the physical and mechanical tests are in general, found to be above the threshold acceptance values suggested by the American and Turkish Standards for the use of marbles as a building stone and in the same order as the properties of Italian (Carrara) and Greek marbles reported in the literature. Additionally, the mean test values of the marbles have given high correlations with one another and the relations obtained between the index test results determined by simple techniques requiring minimal sample preparation effort and the mean values of the more elaborate engineering tests results are presented as tables and graphs for wider use.     

Microtextural Characteristics and Origin of Dolomites in the Tepearasi Formation, SW of Beysehir-Konya, Turkey

The Tepearasi Formation of the autochthonous Geyikdagi Group in the Central Tauride Belt, SE of Beysehir, is Dogger in age and consists dominantly of massive limestones and greyish dolomites occurring within the middle to upper sections. The total thickness of the dolomitic levels ranges from 100-300 m and laterally extends 500-700 m. Three types of dolomite were distinguished through petrographic analyses: homogeneous, mottled (saddle-crystalline) and joint-filling dolomite, which were interpreted to have formed in two different stages, early diagenetic and late diagenetic. The homogeneous dolomite of the early diagenetic stage is light-coloured and monotonous-textured and shows the form of a dolosparite mosaic. The mottled dolomite formed in the late diagenetic stage is light- to dark-coloured and coarsely granular idiomorphic. The other type of late diagenetic dolomite, described as the joint-filling type, presents a crystal growth pattern from the joint walls towards the centre of the joint space. I