Geometry of co-seismic surface ruptures and tectonic meaning of the 23 October 2011 Mw 7.1 Van earthquake (East Anatolian Region, Turkey)

Transcription

1 Geometry of co-seismic surface ruptures and tectonic meaning of the 23 October 2011 Mw 7.1 Van earthquake (East Anatolian Region, Turkey) Bülent Dogan & Ahmet Karakaș. Journal of Structural Geology, 46(2013), 報告者 : 邱奕維指導教授 : 黃文正老師日期 :2014/12/25 1

2 Outline Introduction Seismicity Co-seismic deformation InSAR and GPS Investigations of surface rupture Main thrust fault surface rupture (MTFSR) Secondary strike-slip fault surface rupture Secondary tensional ground cracks Discussion Seismologic interpretation of the Van earthquake Tectonic origin of all surface rupture Conclusions 2

3 Introduction The Van earthquake (Mw 7.1) took place north of the BZSZ on 23 October (from google earth) 3

4 Seismicity Paleo-earthquake Color Year (AD) Blue 1966~1976 Gray 1968~1977 Orange 1999~2000 Black 1988~2000 Some focal mechanism solutions of both historical and the instrumental period earthquakes around the city of Van over the past 50 years. 4

5 Seismicity 60 km 20 km (Zahradnik and Sokos, 2011) The locations of the epicenters and fault plane solutions calculated by the different international seismological centers. The major thrust fault strike is N60 E and dip is 55 NW with a minor left lateral offset. (Irmak et al, 2012) Distribution of aftershocks (M >2) Subsurface rupture length : 60 km Rupture area: about 2000 km 2 5

6 Co-seismic deformation InSAR GPS (Geohazards, 2011a; ; Fielding, 2012). InSAR COSMO-SkyMed (CSK) interferogram (InSAR) rewrapped with 20 cm color contours showing displacements in the radar line-of-sight (Geohazards, 2011b; Ergintav, 2012) GPS Co-seismic displacement field, based on Turkish CGPS network. 6

7 Co-seismic deformation Main thrust fault surface rupture (MTFSR) 7

8 Co-seismic deformation Rupture length: 8 km Max vertical offset: 0.15m Surface rupture length divided subsurface length: 0.14 With a little left-lateral in MTFSR 8

9 Co-seismic deformation Slip distribution on MTFSR (Irmak et al, 2012) Slip plane with the maximum displacement 3.6 m around the hypocenter (white star) of the earthquake 9

10 Co-seismic deformation Secondary strike-slip fault surface rupture Left-lateral in Kozluca Fault (KF) Right-lateral between the south of Koçköy and the north of Satıbey 10

11 Co-seismic deformation Surface rupture in Kozluca Fault (KFSR) Left lateral strike-slip fault The strike of surface rupture : N5 ~20 E 11

12 Secondary tensional ground cracks a&b Co-seismic deformation c&d 12

13 Co-seismic deformation Tensional ground crack developed during Van earthquake. 13

14 Discussion Are the geometry of main fault offset during Van earthquake consistent with the result Wells and Coppersmith published in 1994? Fault geometry derived from Van earthquake of Mw 7.1: Surface rupture zone (SRL): 8 km (field observation) Subsurface rupture zone (SsRL): 60 km (Irmak et al., 2012) Rupture Area (RA): 2000 km 2 (Irmak et al., 2012) Fault displacement derived from Van earthquake of Mw 7.1: Maximum surface displacement (Max D): 0.15m (field observation) Maximum subsurface displacement (Ss Max D) : 3.6m (Irmak et al., 2012) Average surface displacement (Ave D): 0.08 m Average subsurface displacement (Ave Ss D ): 1.8 m The average surface displacement is about half of the maximum surface displacement (Wells and Coppersmith,1994) 14

15 Discussion Are the geometry of main fault offset during Van earthquake consistent with the result Wells and Coppersmith published in 1994? Mw: 7.1 SsRL: 60 km Mw: 7.1 (USGS,2011a) RA: 2000 km 2 (Wells and Coppersmith,1994) 15

16 Are the geometry of main fault offset during Van earthquake consistent with the result Wells and Coppersmith published in 1994? Mw: 7.1 SRL: 8 km Max D: 0.15m Discussion (Wells and Coppersmith,1994) 16

17 Are the geometry of main fault offset during Van earthquake consistent with the result Wells and Coppersmith published in 1994? Mw: 7.1 Max D: 0.15m Ave Ss Max D : 1.8 m Ave Max D: 0.08 m Discussion (Wells and Coppersmith,1994) 17

18 Discussion Seismologic interpretation of the Van earthquake The surface or near surface parameters are not consistent with the subsurface parameters. The fault plane creating the Van earthquake is possibly a blind thrust. 18

19 Discussion Can the co-seismic rupture created during Van earthquake prove Arabian plate and Eurasia plate are still in collision? Strike-slip faults occur in continental thrust faults belts due to compression. ( 19

20 Discussion Can the co-seismic rupture created during Van earthquake prove Arabian plate and Eurasia plate are still in collision? Tensional ground crack occurred on left-lateral strike-slip faults which triggered during Van earthquake 20

21 Discussion Can the co-seismic rupture created during Van earthquake prove Arabian plate and Eurasia plate are still in collision? Arabian plate and Eurasia plate are still in collision 21

22 Conclusion Since the length of the surface rupture observed in the field does not compensate with the magnitude of the earthquake, the fault can be interpreted as a blind thrust fault. The Van earthquake proved that the collision of Arabian and Eurasian plates still continues on a large scale. 22

23 Thanks for your attention! 23