Properties of the aftershocks sequences of the 2000 and 2002 earthquakes in Aksehir-Afyon graben, west-central Anatolia, Turkey

The b-value of the Gutenberg-Richter's frequency-magnitude relation and the p-value of the modified Omori law, which describes the decay rate of aftershock activity, were investigated for more than 500 aftershocks in the Aksehir-Afyon graben (AAG) following the 15 December 2000 Sultandagi-Aksehir and the 3 February 2002 Cay-Eber and Cobanlar earthquakes. We used the Kandilli Observatory's catalog, which contains records of aftershocks with magnitudes >= 2.5. For the Cobanlar earthquake, the estimated b-values for three aftershock sequences are in the range 0.34 <= b <= 2.85, with the exception of the one that occurred during the first hour (4.77), while the obtained p-values are in the range 0.44 <= p <= 1.77. The aftershocks of the Sultandagi earthquake have a high p-value, indicating fast decay of the aftershock activity. A regular increase of b can be observed, with b < 1.0 after 0.208 days for the Cay-Eber earthquake. A systematic and similar increase and decrease pattern exists for the b- and p-values of the Cobanlar earthquakes during the first 5 days

Major neotectonic features of eastern Marmara region, Turkey: development of the Adapazari-Karasu corridor and its tectonic significance

Eastern Marmara region consists of three different morphotectonic units: Thrace-Kocaeli Peneplain (TKP) and Camdag-Akcakoca Highland (CAH) in the north, and Armutlu-Almacik Highland in the south of the North Anatolian Fault Zone (NAFZ). The geologic-morphologic data and seismic profiles from the Sakarya River offshore indicate that the boundary between the TKP in the west and 1 CAH in the east is a previously unrecognized major NNE-SSW-trending strike-slip fault zone with reverse component. The fault zone is a distinct morphotectonic corridor herein named the Adapazari-Karasu corridor (AKC) that runs along the Sakarya River Valley and extends to its submarine canyon along the southern margin of the Black Sea in the north. It formed as a transfer fault zone between the TKP and CAH during the Late Miocene; the former has been experiencing extensional forces and the latter compressional forces since then. East-West-trending segments of the NAFZ cuts the NE-SW-trending AKC and their activity has resulted in the formation of a distinct fault-bounded morphology, which is characterized by alternating E-W highlands and lowlands in the AKC. Furthermore, this activity has resulted in the downward motion of an ancient delta and submarine canyon of the Sakarya River in the northern block of the NAFZ below sea level so that the waters of the Black Sea invaded them. The NE-SW-trending faults in the AKC were reactivated with the development of the NAFZ in the Late Pliocene, which then caused block motions and microseismic activities throughout the AKC. Copyright (C) 2004 John Wiley Sons, Ltd