et al. Earth, Planets and Space (2017) 69:107
Electrical conductivity of a locked fault:
investigation of the Ganos segment of the
North Anatolian Fault using three-dimensional
, Sabri Bülent Tank
and Sinan Özaydın
This study attempts to reveal the fault zone characteristics of the locked Ganos Fault based on electrical resistivity
studies including audio-frequency (AMT: 10,400–1 Hz) and wide-band (MT: 360–0.000538 Hz) magnetotellurics near
the epicenter of the last major event, that is, the 1912 Mürefte Earthquake (M
7.4). The AMT data were collected
at twelve stations, closely spaced from north to south, to resolve the shallow resistivity structure to 1 km depth.
Subsequently, 13 wide-band MT stations were arranged to form a grid enclosing the AMT proﬁle to decipher the
deeper structure. Three-dimensional inverse modeling indicates highly conductive anomalies representing fault zone
conductors along the Ganos Fault. Subsidiary faults around the Ganos Fault, which are conductive structures with
individual mechanically weak features, merge into a greater damage zone, creating a wide ﬂuid-bearing environment.
This damage zone is located on the southern side of the fault and deﬁnes an asymmetry around the main fault strand,
which demonstrates distributed conduit behavior of ﬂuid ﬂow. Ophiolitic basement occurs as low-conductivity block
beneath younger formations at a depth of 2 km, where the mechanically weak to strong transition occurs. Resistive
structures on both sides of the fault beneath this transition suggest that the lack of seismicity might be related to the
absence of ﬂuid pathways in the seismogenic zone.
Keywords: Fluid, North Anatolian Fault, Ganos Fault, Fault zone conductor, Locked fault, Electrical resistivity,
Asymmetric damage zone, Magnetotellurics
© The Author(s) 2017. This article is distributed under the terms of the Creative Commons Attribution 4.0 International License
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and indicate if changes were made.
e Ganos Fault is an active segment representing a seis-
mic gap at the western end of the 1200-km-long dex-
tral North Anatolian Fault (NAF; Şengör et al. 2005). In
Northwest Anatolia, the NAF exhibits a relatively com
plex structure; it partitions into several active branches
as it enters the Marmara Sea near İzmit. e northern
most strand exits the sea near Gaziköy, Tekirdağ, before
it enters the Saros Bay. is particular 45-km-long seg
ment is known as Ganos Fault (GF) and generated the
7.4 Şarköy–Mürefte Earthquake in 1912 (Ambraseys
and Finkel 1987; Ambraseys 2002). Major activities along
the NAF had the tendency to propagate from east to west
due to the generation of periodical seismic events with
centennial cycles (Parsons et al. 2000; Şengör et al. 2005).
Following the disastrous 1999 İzmit and Düzce earth
quakes, the geoscience community reached a consensus
that the next signiﬁcant event is expected in the western
part of the NAF, particularly related to segments within
the Marmara Sea and/or GF (Şengör et al. 2005).
e GF was previously examined using geologi
cal, geodetic, and seismological tools (Okay et al. 1999;
Rockwell et al. 2001; Yaltırak and Alpar 2002; Okay et al.
2004; Seeber et al. 2004; Motagh et al. 2007; Janssen et al.
2009; Okay et al. 2010; Özcan et al. 2010; Öztürk et al.
2015) to decipher its tectonic evolution, morphologi
cal and structural properties, and fault–ﬂuid relations.
Kandilli Observatory and Earthquake Research Institute, Boğaziçi
University, İstanbul, Turkey
Full list of author information is available at the end of the article