Source mechanism of the 2000 November 15 Lake Van earthquake (M_w= 5.6) in eastern Turkey and its seismotectonic implications

Abstract

SUMMARY Detailed source process of the 2000 November 15 Lake Van (eastern Turkey) earthquake (Mw= 5.6) was retrieved using the method of Kikuchi & Kanamori for source inversion of complex body waveforms. The event has been reported by USGS as a deep (67 km) subcrustal earthquake resulting from a rupture on a normal fault beneath the Bitlis Suture zone where continental collision is in action between the Arabian and Eurasian plates. However, our source model based on the analysis of complex body‐waveforms suggests that the earthquake is a shallow crustal event comprised of two subevents on a predominantly reverse fault at depths of 12.5 and 15 km with a time interval of about 18 s. The seismic moment of the second subevent (Mo= 1.6 × 1017 Nm; strike = 76°, dip = 55° and rake = 120°) is larger than the first subevent (Mo= 1.0 × 1017 Nm; strike = 87°, dip = 62° and rake = 110°). Visual inspection of the strong ground motion records and waveform inversion analysis of the near‐field records from four broad‐band stations confirm the occurrence of the two subevents at shallow depths. We examined whether or not the observed complex waveforms of the main shock can be modelled in terms of a single point source embedded at an intermediate depth, and the result turned out to be further evidence for the multiple rupture. The plausibility of the focal depths and mechanisms of the two subevents was also examined by retrieving the source parameters of 14 aftershocks from near‐field waveform data. Most of the aftershocks were relocated at depths around 15 km, which agrees with the shallow main shock. In addition, the analysis of near‐field waveform data indicates subcrustal earthquake activity neither in the source region of the Lake Van earthquake nor in the Turkey–Iran border region. In the Turkey–Iran border region, an event on 1999 February 19 was reported to have taken place at a depth of 66 km (USGS) and 77 km (ISC), which also conflicts with our focal depth (18 km) determined through CMT inversion analysis of the broad‐band records at the station GNI.

23 Ekim 2011 VAN Depreminin (Mw=7.1) Oluşturduğu Coulomb Gerilme Değişimi

“…Optimum yönlenmiş fay üzerinde gerilme değişim hesapları öncelikle asal gerilme eksenleri yönelimleri ile bölgesel gerilme alanının tanımlanmasını gerektirir. Buna göre, bu çalışmada [16] tarafından verilen bölgesel gerilme alanı (σ1 için, azimuth=335…”

8 January 2013 Mw = 5.7 North Aegean Sea earthquake and its seismotectonic significance

“…When the principal stress axis, σ 3 , is vertical and Σ2 is horizontal, stress field is defined by a reverse faulting type (Twiss & Moores, 1992). More detailed information about R (shape factor) is given by Bellier and Zoback (1995) and Pınar et al (2007). The regional stress tensor analysis for the shape and orientation of the stress tensor calculated from 30 fault plane (totally 30; 7 earthquakes since 1672 plus the 8 January 2013 earthquake and its 22 aftershocks) solutions (Figure 7(a) and (b)).…”

Coulomb static stress changes before and after the 23 October 2011 Van, eastern Turkey, earthquake (<i>M</i><sub>W</sub>= 7.1): implications for the earthquake hazard mitigation

“…Local tectonic features, epicentral distribution of large earthquakes (red and green stars) and available focal mechanisms (blackwhite beach balls) for the Lake Van area along with the bathymetry of Lake Van. Extent of faults are from Wong and Finckh (1978), Koçyigit et al (2011) andMTA (2012), focal mechanisms are from McKenzie (1972), Pınar (1995), Pınar et al (2007), Utkucu (2013a) and USGS-NEIC and the bathymetry of Lake Van is from Wong and Degens (1978). See Table 2 2004).…”

“…The earthquake focal mechanisms of the recent earthquakes in the area have indicated that the type of faulting along the boundary faults is mainly thrusting (Fig. 2) (Pınar et al, 2007;Utkucu, 2013a). Pınar et al (2007) performed a stress tensor inversion of the available focal mechanisms and found that the stress regime was transpressive with a maximum compression axis roughly in the N-S direction.…”

“…2) (Pınar et al, 2007;Utkucu, 2013a). Pınar et al (2007) performed a stress tensor inversion of the available focal mechanisms and found that the stress regime was transpressive with a maximum compression axis roughly in the N-S direction. The presence of active thrusting in the area was inarguably evidenced by the occurrence of the 23 October 2011 Van earthquake, which was produced by the Van fault (VF) Emre et al, 2011;Akyüz et al, 2011;Gülen et al, 2012).…”