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8th Congress of the Balkan Geophysical Society
- Conference date: October 5-8, 2015
- Location: Chania, Greece
- Published: 05 October 2015
121 - 124 of 124 results
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Crustal Structure beneath Central Anatolia from Receiver Functions
More LessSummaryThe receiver function analysis method was implemented to determine the crustal structure around Ankara, Central Anatolia. Teleseismic earthquake records are used in this method which is based on the conversion of incident P waves into S waves reaching an interface in the crust or upper mantle and arrival of the converted wave to the station just after the direct P waves. A temporary seismic network, Ankara Earthquake Monitoring Network, consisting of six broad-band seismograph stations has been deployed to monitor the seismicity in Ankara and vicinity in the period 2007–2010. In this study, the crustal thicknesses beneath AnkNET stations were calculated. The stations between latitudes 39° – 41°N and longitudes 32° –34°E were located about 100 km apart from each other through a circle with radius about 100 km, including one in Ankara. Hypocentral parameters of 43 earthquakes which are equal or greater than an instrumental magnitude of 6.5 occurred at a distance between 30°–100° far from the central coordinates of AnkNET (40°N, 33°E) were retrieved from IRIS earthquake catalogue. According to the results of the study, the crustal thickness of the region ranges from 32.8 km to 39.05 km with an average of about 35.66 km.
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Spatial Variations of Seismotectonic b and Dc-values in and around the East Anatolian Fault Zone (EAFZ), Turkey
More LessSummaryAn evaluation of recent seismicity behaviors in the East Anatolian Fault Zone, eastern part of Turkey, is made by using Gutenberg-Richter b-value and fractal dimension Dc-value. Reasenberg’s algorithm is used in order to separate the dependent events from independent ones. The completeness magnitude in study region is calculated as 2.8. b-value is calculated as 1.02+/−0.01 by maximum likelihood estimation and matches the Gutenberg-Richter law with a b-value typically close to 1. Dc-value is found as 2.34+/−0.04 with 95% confidence limit by linear regression and this large value suggest that seismicity is more clustered at larger scales in the East Anatolian Fault Zone. The smallest b-values and the highest Dc-values are found in the same areas covering the East Anatolian Fault Zone, Aşkale Fault, Sancak-Uzunpınar Fault Zone, Pülümür Fault, Göynük Fault Zone and Genç Fault, in and around Karataş-Osmaniye Fault Zone and in the southeast part of the study region. Thus, low b-value in these regions may be an indication of low degree of heterogeneity, high-strain due to the active tectonics and stress to build up over time and to be released by events. Thus, special attention should be given to these regions where low b-value and large Dc-value are observed.
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First Result of the Seismic Monitoring of Mecsek Mountains
Authors A.CS. Attila Csaba, E. Bujdoso, R. Csabafi, E. Hegedűs, I. Török and I. TóthSummaryThe Geological and Geophysical Institute of Hungary deployed a continuously operating seismic monitoring network in the Mecsek Mountains in August 2004. The main aim was to monitor the neotectonic activity and geodynamic processes in the western Mecsek Mountains and particularly in the Boda Siltstone Formation which is the possible target of the high activity nuclear waste deposit. The primary aim of the study was the detection of small and very small magnitude seismic signals. 31 stations were deployed within a circle with radius of about 50km in the Mecsek Mountains, around the village of Boda. The stations in the network are self-developed with big memory capacity and continuous GPS synchronised time, small size and low energy. We determined 176 earthquakes with magnitude between 2.8 and -0.8 from August 2004 to 31 December 2013. According to our observations microseismic events are frequent in some specific geologic-tectonic territory: Events linked with Mecsekalja-zone follow its WSW-ENE strike. Earthquakes along the Dráva River, in the distance of approx. 20 km from the study area. Earthquakes in the area of Kővágószőlős-Bakonya-Boda, which may be linked with earlier mining activity. We marked several smaller sources where we determined 5–10 earthquakes.
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Initial Results from the Central Anatolian Seismic Experiment: Local Seismicity and Shear Wave Splitting
Authors N. Turkelli, M. Kahraman, M.U. Teoman, G. Polat, R. Polat, D. Kalafat, M. Ozer and O. CokSummaryIn order to create high-resolution images of the crust and upper mantle in central Anatolia, we deployed a 2-year 71 station broadband embedded the Kandilli Observatory and Earthquake Research Institute (KOERI) of Bogazici University national seismic network.
This study focuses on crust and upper mantle studies such as earthquake locations (especially micro-seismic activity) and shear wave splitting (SKS) analysis.
Distribution of earthquake locations supports the presence of seismic activity partly localized along major tectonic structures. The CAFZ, generally considered to be less seismically active, shows a significant amount of seismic activity that is consistent with internal plate deformation. Additional seismicity is observed near volcanically active regions of central Anatolia. We found that velocities for the crust and uppermost mantle are; P waves 6.01 km/s, and 8.21 km/s, and for S waves 3.89 km/s, and 4.64 km/s, respectively.
The shear-wave splitting analysis has been carried out on teleseismic data acquired by CD-CAT stations mainly from May-2013 to 2014. The averaged fast polarization directions in the EAFZ are fairly uniform and show NE-SW orientations, but they are well aligned with the EAFZ. Rapid spatial variations in splitting parameters are observed at the stations located in the Adana region.
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