Crustal structure and local seismicity in western Anatolia

Abstract

S U M M A R YWestern Anatolia is one of the most seismically active continental regions in the world and much of it has been undergoing NS-directed extensional deformation since Early Miocene time. In a cooperative study, seismologists from Saint Louis University, USA and Dokuz Eylül University, Turkey, deployed five broad-band and 45 short-period seismic stations in western Anatolia between 2002 November and 2003 October. The present paper uses data collected by this network and the data from five permanent stations operated by the Kandilli Observatory and Earthquake Research Institute to map the hypocentral distribution of local earthquakes and to determine crustal structure of western Anatolia. We obtained a 1-D P-wave crustal velocity model using a generalized scheme for simultaneously obtaining earthquake locations and a crustal velocity model. Our velocity model is characterized by crustal velocities that are significantly lower than average continental values. The low velocities may be associated with high crustal temperatures, a high degree of fracture, or the presence of fluids at high pore pressure in the crust. We located 725 local earthquakes and classified them in three categories. We found that the level of seismic activity in western Anatolia is higher than previously reported. Station delays resulting from the inversion process correlate with near-surface geology and the thickness of sediments throughout the region. The hypocentral distribution of the events indicates that peak seismicity for the region occurs at depths of about 10 km.

Tectonic analysis of the Honaz Fault (western Anatolia) using geomorphic indices and the regional implications

“…The length of the Honaz Fault, which is similar to the thickness of the seismogenic layer in the region (e.g. 10 km, Akyol et al, 2006), and results of the calculated geomorphic indices in this study indicate that Honaz Fault is an E-W-trending active normal faults with the potential to cause an earthquake with a magnitude of 6.7 in western Anatolia.…”

Seismotectonic content by the source parameters of the 10 June 2012 Ölüdeniz-Fethiye (Dodecanese Islands) Mw 6.1 earthquake and aftershocks (southwestern Turkey)

“…4c). In the total slip Table 1 Adopted and modified layered crustal seismic velocity structure (Akyol et al 2006) a, b = P and S wave velocities, distribution, a large asperity area can be seen in 2-3 km beneath the hypocentral area of the fault plane. The rupture is complex and gradually propagates from the hypocenter to southwest.…”

“…The sampling time of the Green's function was set at 0.5 s. The layered seismic velocity structures used in the synthetics are given in Table 1. For a near-structure, we adopted the velocity model of Akyol et al (2006) with small modifications and with an additional layer of 1.5 km thick water.…”

The 10 June 2012 Fethiye Mw 6.0 aftershock sequence and its relation to the 24–25 April 1957 Ms 6.9–7.1 earthquakes in SW Anatolia, Turkey

“…(For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.) functions are generated using the discrete wavenumber method (Bouchon, 1979), assuming the crustal structure model of Akyol et al (2006) for the calculation. The synthetics are calculated for a horizontally layered structure given in Table 1.…”