Frequency-dependent body-Q and coda-Q in Karlıova Triple Junction and its vicinity, eastern Turkey

Authors: ALPER DEMİRCİ

Abstract: A dataset obtained from six broadband stations of 111 small- to moderate-sized local events that occurred between 2010 and 2018 was analyzed to reveal the frequency-dependent seismic body (body-Q) and coda (coda-Q) wave attenuation characteristics of three tectonic branches of the Karlıova Triple Junction: the Varto Fault Zone (VFZ), North Anatolian Fault Zone (NAFZ), and East Anatolian Fault Zone. The magnitude range was between 2.8 and 6.1 with shallow (<10 km) focal depths. The maximum station-event distance was selected as not to exceed 120 km. Frequency-dependent Qc functions were determined using the single back-scattering model with four lapse time lengths (20, 30, 40, 50 s) while the extended coda normalization method was performed to estimate the body wave attenuation functions for seven central frequencies varying from 1.5 Hz to 18 Hz. The minimum and maximum Qp values were 7 at 1.5 Hz for the VFZ and 739 at 18 Hz for the NAFZ, respectively. Q_s values were observed between a minimum of 26 for VFZ and maximum of 1259 for NAFZ. Additionally, coda-Q results show a strong lapse time dependency between Q₀ and n; exhibiting a decrease in n by an increase in Q0, with an ascending lapse time. Comparing the three subregions of the Karlıova Triple Junction, VFZ appears to have a significantly higher attenuation for all Q types and Qs/Qp ratios while the NAFZ has relatively low attenuation.

Keywords: Attenuation, coda normalization method, single backscattering model, Karlıova Triple Junction, Turkey

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