Jeofizik

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Browsing Jeofizik by Subject "Earth -- Crust."

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    Crust and upper-mantle imaging by using P and S receiver functions in different tectonic regimes
    (Thesis (Ph.D.)-Bogazici University. Kandilli Observatory and Earthquake Research Institute, 2015., 2015.) Kahraman, Metin.; Türkelli, Niyazi.
    P and S receiver functions (RF) are effective tools to solve crustal and upper-mantle velocity contrasts. In this respect, RFs are utilized to image three different tectonic regimes of Anatolia. Firstly, western segment of the North Anatolian Fault Zone (NAFZ) is inspected by data from a dense broadband network (Dense Array for North-Anatolia - DANA) of 71 seismic stations with a nominal station spacing of 7 km in the vicinity of the 1999 Izmit earthquake. High resolved 2-D cross-section images reveal previously unkown small-scale structures and fault geometries in the crust and upper-mantle. Secondly, N-S extension dominated Western Anatolia (WA) is observed by 47 permanent broad-band stations. Totally, 3563 high signals to noise ratio P wave RFs with cut-off frequency of ~1 Hz are obtained among 43146 teleseismic earthquakes. Crustal differences, sharp Moho changes and low velocity zones are defined by 2-D cross-sections in the region. Lastly, Isparta Angle (IA) is imaged by data from a temporary and permanent broad-band seismic network that is composed 42 seismic stations. 4501 P wave RFs are used to resolve upper crustal and Moho depths and 946 S wave RFs are operated to figure out lithosphericasthenospheric boundary (LAB). Migrated P wave RFs cross-sections present Moho anomalies and African slab in the crust of IA. On the other hand, migrated S wave RFs cross-sections show variation of LAB boundary between ~50 to ~90 km depth range.
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    Crustal structure of the Isparta Angle and surrounding regions using p-receiver function analysis
    (Thesis (M.S.)-Bogazici University. Kandilli Observatory and Earthquake Research Institute, 2008., 2008.) Kahraman, Metin.; Türkelli, Niyazi.
    Isparta Angle is located on southwestern Turkey and has a complex structure which is a consequence of collision between African and Anatolian plates. In order to further understand this complexity, we deployed a temporary network consisting of nineteen broad band instruments in addition to KOERI’s permanent seismic stations in the region. Crustal velocity and Moho depth variation were figured out along north – south and east – west profiles formed by fourteen temporary and permanent stations. We implemented two different receiver function methods to the recorded events. Firstly, we applied joint inversion of receiver functions and surface wave group velocities in order to model lithospheric velocity structure of the region. Receiver functions are sensitive to shear wave velocity contrast and vertical travel times, however surface wave dispersion curves are sensitive to shear wave velocity averages. Combining these different properties of shear waves may bridge resolution gaps associated with each individual data set. Secondly, Moho depth was calculated by applying H-K stacking algorithm. We found that the shear velocities for crustal and upper mantle thicknesses vary between 1.95-4.05 and 4.09-4.14 km/s, respectively, and in addition to this, Moho depth is varying between 30.5 and 40.7 km. beneath stations on the east – west profile. On the other hand, the shear velocities for crustal and upper mantle thicknesses vary between 1.41-4.05 and 3.97-4.23 km/s respectively, and the calculated Moho depth is between 35.5 and 47.0 km. beneath stations located on the north – south profile. Compared to the other geophysical studies done in the same region, this is the first study to understand unusual aspect of Isparta Angle.