The North Anatolian Fault (NAF) is one of the world&rsquo / s largest active continental strikeslip
faults, and forms the northern margin of the Anatolian plate. Although its geologic
and geomorphologic features are well defined, crustal deformation and associated
seismicity around central segment of the NAF is relatively less-known. In this study, we
analyzed locations and focal mechanisms of 172 events with magnitude &ge / 3, which are
recorded by 39 broadband seismic stations deployed by the North Anatolian Passive
Seismic Experiment (2005-2008). Distribution of the events shows that the local
seismicity in the area is widely distributed, suggesting a widespread continental
deformation, particularly in the southern block. For the entire data set, P- and S- arrival
times are picked and events are relocated using the HYPOCENTER program. Then,
relocated events which have a good azimuthal coverage with a maximum gap of 120° / and at least 13 P- wave readings are selected and 1-D inversion algorithm, VELEST, is
used to derive the 1-D seismic velocity model of the region. The final model with
updated locations is later put together to the FOCMEC program, to obtain focal
mechanisms solutions. In this step, an iterative scheme is applied by increasing the
number of data errors. To obtain more unique solutions, first motions of P and SH
v
phases are used along with SH/P amplitude ratios. Resultant 109 well-constrained focal
mechanisms later used to perform stress tensor inversion across the region.
Our focal mechanisms suggest a dominant strike-slip deformation along two major fault
sets in the region. In the east, E-W trending splays (Ezinepazari, Almus, and Laç / in
Kizilirmak) show right-lateral strike-slip motion similar to the NAF whereas in the west,
N-S trending faults (Dodurga, Eldivan) show left lateral strike-slip motion. Overall,
stress orientations are found as: maximum principal stress, &sigma / 1, is found to be
subhorizontal striking NW-SE, the intermediate principle stress, &sigma / 2, is vertically
orientated and the minimum principal stress, &sigma / 3, is found to be NE &ndash / SW striking,
consistent with the strike-slip regime of the region.
| Identifer | oai:union.ndltd.org:METU/oai:etd.lib.metu.edu.tr:http://etd.lib.metu.edu.tr/upload/12612214/index.pdf |
| Date | 01 July 2010 |
| Creators | Karasozen, Ezgi |
| Contributors | Ozacar, Arda A. |
| Publisher | METU |
| Source Sets | Middle East Technical Univ. |
| Language | English |
| Detected Language | English |
| Type | M.S. Thesis |
| Format | text/pdf |
| Rights | To liberate the content for public access |
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