ÖNCEL AKADEMİ: MÜHENDİSLİK BİLİMLERİ
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1) The document analyzes seismicity and GPS data in western Turkey to examine correlations between geodetic strain and earthquake hazard. 2) Key results include a positive correlation between seismic clustering and the b-value along the Northern Anatolian Fault Zone. No correlation was found between seismicity measures and GPS strain overall. 3) In the extensional region, seismic clustering positively correlates with dilatation at scales of 10-40km, suggesting increased extension produces more dispersed seismicity.
ÖNCEL AKADEMİ: MÜHENDİSLİK BİLİMLERİ
- 1. Mühendislik Bilimlerinde Özel Konular MUBİ9035 - Mühendislik Bilimleri Bölümü İstanbul Üniversitesi
- 2. A FRICAN PLA TE 8 BLACK SEA 3 1 2 4 9 8 7 6 5 13 12 11 10 15 14 1617 18 19 20 21 24 M>2.9 h< 39km 1981-1988 Shear Zone Extensional Zone Compressional Zone GPS control points 23 24 25 26 27 28 29 30 31 33 34 35 36 37 38 39 40 41 42 43 Mw 6.4 1995 Mw 5.8 1997 Mw 6.6 1982 Mw 6.6 1983 Mw 6.8 1981 Mw 6.2 1996 Mw 5.6 1996 25 Mw 5.5 1994 22 23 23 24 25 26 27 28 29 30 31 33 34 35 36 37 38 39 40 41 42 43 23 8 7 6 12 11 15 17 18 19 20 21 24 25 2 3 22 23 1 4 9 13 5 10 14 16 0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 Shear Strain nstrain/a 23 24 25 26 27 28 29 30 31 33 34 35 36 37 38 39 40 41 42 43 -70 -60 -50 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90 100 110 8 7 6 12 11 15 17 18 19 20 21 24 Compr. Extens. nstrain/a 25 2 3 22 23 1 4 9 13 5 10 14 16 Contour maps of GPS derived shear and dilatation are shown in the maps above (middle and right maps, respectively). GPS strains were derived by Kahle et al. (2000) from GPS velocity data presented by McCloskey et al. (2000) for the western Turkey and eastern Mediterranean area examined in this paper. Average shear and dilatation in each seismic zone were estimated by averaging contour values of shear and dilatation observed on the regular grid of points highlighted in the map above. GPS control points are shown along with events of magnitude M>3.0 recorded between 1981 and 1998. The 25 seismic zones into which the area was subdivided for analysis and comparison are also outlined. Geodetical strain and earthquake hazard: Example from western Turkey
- 3. AFR ICAN PLA TE 8 BLACK SEA 3 1 2 4 9 8 7 6 5 13 12 11 10 15 14 1617 18 19 20 21 24 M >2.9 h< 39km 1981-1988 Shear Zone Extensional Zone Compressional Zone GPS control points 23 24 25 26 27 28 29 30 31 33 34 35 36 37 38 39 40 41 42 43 Mw 6.4 1995 Mw 5.8 1997 Mw 6.6 1982 Mw 6.6 1983 Mw 6.8 1981 Mw 6.2 1996 Mw 5.6 1996 25 Mw 5.5 1994 22 23 D2 D15 D2 D15 D2 D15 b ML- MU Shea r Dilita tion1 1.44 1.1 1.73 1.22 1.4 1.01 1.51 2.6-5.0 161.79 19.38 2 1.43 1.07 1.81 1.33 1.43 1.12 1.39 2.6-5.5 201.07 3.63 3 1.62 1.42 1.9 1.28 1.49 1.26 1.47 3.1-4.8 164.82 12.88 4 1.24 0.84 1.86 1.5 1.02 0.64 1.11 3.5-6.0 191.60 25.85 7 1.53 1.24 1.94 1.48 1.48 1.23 1.24 3.2-6.0 101.71 55.87 8 1.32 0.86 1.85 1.13 1.37 0.92 1.16 3.2-4.9 189.45 3.88 9 1.18 0.83 1.86 1.4 1.14 0.64 0.97 3.0-5.3 146.38 11.55 5 1.07 0.73 1.85 1.59 0.95 0.57 1.75 2.6-4.7 41.02 36.21 6 1.33 0.92 1.81 1.56 1.22 0.78 1.81 2.7-4.8 78.75 33.68 10 0.89 0.58 1.46 0.95 0.87 0.46 1.35 3.0-4.8 70.32 44.69 11 1.48 1.2 1.83 1.37 1.53 1.24 1.39 3.0-5.8 102.35 40.96 12 1.52 1.26 1.89 1.37 1.53 1.39 1.5 3.2-5.1 72.75 75.83 13 1.36 1 1.86 1.71 0.75 0.41 1.1 3.1-5.5 89.26 25.51 14 1.4 1.08 1.79 1.26 1.4 1.19 1.32 2.9-5.5 78.81 53.66 15 1.57 1.26 1.93 1.36 1.59 1.31 1.28 3.1-5.4 78.25 54.39 16 1.38 0.99 1.42 0.97 1.24 0.94 1.4 3.1-5.4 47.99 38.12 17 1.42 1.05 1.78 1.44 1.37 1 1.22 3.2-5.4 50.59 37.22 18 1.61 1.32 1.9 0.81 1.64 1.43 1.25 3.6-4.9 58.89 80.91 19 1.43 1.18 1.88 1.16 1.2 0.88 0.67 3.5-5.2 38.75 22.09 20 1.74 1.5 1.81 1.04 1.77 1.64 1.44 3.5-5.3 68.88 20.76 21 1.44 1.09 1.79 1.51 0.92 0.55 1.21 3.7-5.0 95.04 18.27 22 1.68 1.38 1.87 1.12 1.63 1.39 1.49 3.2-4.6 54.22 10.21 23 1.63 1.04 1.82 1.27 1.61 0.99 1.24 3.8-5.7 107.79 -22.87 24 1.65 1.23 1.57 0.93 1.75 1.47 1.08 3.7-5.5 103.39 -40.39 25 1.45 1.09 2 1.07 1.55 1.08 1.21 3.5-5.8 75.28 -16.12 The study area was divided into three regional tectonic subdivisions consisting of a region of shear in the north associated with the Northern Anatolian Fault Zone (NAFZ), a region dominated by extension in the back-arc region of central Turkey, and a region of compression along the Aegean subduction zone. Seismotectonic parameters (Dq and b) and geodetic strains (shear and dilatation) are shown in the table at right for each of the 25 seismic zones. Local Variations of Complex Variables
- 4. D2 D15 D2 D15 D2 D15 b Shear Dilitation 1.43/1.39 1.07/1.05 1.86/1.85 1.33/1.33 1.4/1.33 1.01/0.97 1.24/1.26 164.8/165.3 12.88/19 1.41/1.37 1.06/1.05 1.84/1.78 1.36/1.29 1.3/1.27 0.97/0.97 1.34/1.34 71.54/67.3 39.5/45.3 1.64/1.6 1.16/1.22 1.82/1.81 1.1/1.16 1.62/1.54 1.24/1.19 1.23/1.28 85.16/84.1 -3/-5 Median/mean values of multifractal correlation dimensions D2 and D15 are tabulated for the full range, 2 to 10km range and 10 to 40 km range for each tectonic subdivision of the study area (shear, extension, and compression). The median/mean values of b, shear, and dilatation are also listed for each tectonic region. Over the full range: D2 measured in the region of compression is statistically greater than D2 in the regions of extension and shear. D15 is less than D2 in all cases. Over the 2-10 km scale: Statistically significant differences between regions are not observed. Over the 10-40km scale: The larger value of D in the region of compression suggests that differences observed over the full range are primarily associated with variations occurring at larger 10-40km scales. Regional comparison between seismicity and GPS strain
- 5. The correlation coefficient, r = 0.81 The probability (p) that the slope of the regression line could actually be zero is 0.026 in this case. D 1.1 1.2 1.3 1.4 1.5 1.6 1.7 b 0.7 0.9 1.1 1.3 1.5 1.7 95% confidence band Cross-plot of b values and D2 from the Northern Anatolian Fault Zone
- 6. D2 D15 b Shear Dilat D2 D15 b Shear Dilat D2 D15 b Shear Dilat D2 0.97 0.81 -0.29 0.28 0.5 -0.39 -0.49 0.49 0.96 0.74 -0.26 0.08 D15 0 0.75 -0.38 0.31 0.25 -0.4 -0.39 0.65 0 0.77 -0.28 0.23 b 0.03 0.05 -0.1 -0.06 0.39 0.37 -0.1 -0.06 0.06 0.05 -0.1 -0.06 Shear 0.52 0.4 0.83 -0.79 0.26 0.39 0.83 -0.79 0.57 0.54 0.83 -0.79 Dilat 0.55 0.5 0.9 0.03 0.26 0.12 0.9 0.03 0.86 0.63 0.9 0.03 •Over the full range: A significant positive correlation is observed between seismic clustering (D) and the Gutenberg-Richter b value along the NAFZ strike slip zone. •Over the 10 -40 km scale: A nearly significant relationship between b and D is observed (r = 0.74, p = 0.06) and suggests that the relationship is primarily associated with deeper or regional scale seismicity since significant correlation is not observed over the 2 to 10 km scale. •No correlation was observed between seismicity ( b, D2, D15) and GPS strain. Correlation between seismicity and GPS strain
- 7. Positive Correlation Negative Correlation Low-magnitude events (Preshocks) Large-magnitude events Afterthoughts on the Izmit Earthquake Increased b and decreased DC suggest that the rise in the level of low magnitude seismicity and high intensity clustering along the western portion of NAFZ did not completely release stress transferred into this segment of the fault zone (Oncel et al., 1995, Non.Lineer.Geophysics; Oncel and Wilson, 2001, BSSA). This combination of factors - westward migration along with increased levels of low magnitude seismicity and higher intensity seismic clustering - are indicators of increased seismic risk in the area.
- 8. D2 D15 b Shear Dilat D2 D15 b Shear Dilat D2 D15 b Shear Dilat D2 0.98 -0.29 0.18 0.4 0.48 -0.13 0.18 0.2 0.98 0 0.13 0.67 D15 0 -0.38 0.18 0.46 0.12 0.28 0.31 -0.44 0 -0.05 0.15 0.73 b 0.36 0.23 0.18 0.21 0.69 0.38 0.18 0.21 1 0.88 0.18 0.21 Shear 0.57 0.59 0.57 0.13 0.57 0.34 0.57 0.13 0.68 0.65 0.57 0.13 Dilat 0.19 0.13 0.51 0.67 0.54 0.15 0.51 0.67 0.02 0.01 0.51 0.67 •Over the 2-10 km scale: Significant correlation is not observed between seismic clustering and dilatation. •Over the full range: Significant correlation between b and D is not observed. •Over the 10 -40 km scale: In this subdivision, seismic clustering (D2 and D15) correlate positively with dilatation (r = 0.67 and 0.73 with p = 0.02 and 0.01 respectively). The correlations suggest that increased rates of extension produce increasingly dispersed seismicity. Correlation between seismicity and GPS strain
- 9. D2 D15 b Shear Dilat D2 D15 b Shear Dilat D2 D15 b Shear Dilat D2 0.76 0.51 -0.25 0.03 0.21 0.44 -0.54 0.38 0.9 0.22 -0.22 -0.41 D15 0.08 0.71 -0.68 0.47 0.69 -0.02 0.26 0.46 0.01 0.39 -0.44 -0.1 b 0.3 0.12 -0.83 0.73 0.38 0.97 -0.83 0.73 0.68 0.45 -0.83 0.73 Shear 0.64 0.14 0.04 -0.6 0.26 0.62 0.04 -0.6 0.68 0.39 0.04 -0.6 Dilat 0.96 0.34 0.1 0.21 0.46 0.37 0.1 0.21 0.43 0.84 0.1 0.21 •One would expect seismicity to correlate moreso with dilatation in a subduction zone. However, dilatation along the subduction zone is on average only slightly negative. •Dilatation is positive in the areas to the northeast (17 nstrain/a) and negative (-29 nstrain/a) farther west along the subduction zone. This combination of positive and negative dilatation along the subduction zone is probably responsible for the lack of a more significant correlation between b and dilatation. •The change of dilatation from positive to negative as one goes east to west along the subduction zone suggests a transition in plate interaction from transtensional to transpressive. •Over the full range: Variations of b value correlate negatively with shear (r = -0.83, p = 0.04) in the zones of this subdivision. The correlation of b to dilatation is weakly positive (r = 0.73, p = 0.1). Correlation between seismicity and GPS strain
- 10. D2 D15 b Shear Dilat D2 D15 b Shear Dilat D2 D15 b Shear Dilat D2 0.76 0.51 -0.25 0.03 0.21 0.44 -0.54 0.38 0.9 0.22 -0.22 -0.41 D15 0.08 0.71 -0.68 0.47 0.69 -0.02 0.26 0.46 0.01 0.39 -0.44 -0.1 b 0.3 0.12 -0.83 0.73 0.38 0.97 -0.83 0.73 0.68 0.45 -0.83 0.73 Shear 0.64 0.14 0.04 -0.6 0.26 0.62 0.04 -0.6 0.68 0.39 0.04 -0.6 Dilat 0.96 0.34 0.1 0.21 0.46 0.37 0.1 0.21 0.43 0.84 0.1 0.21 •One would expect seismicity to correlate moreso with dilatation in a subduction zone. However, dilatation along the subduction zone is on average only slightly negative. •Dilatation is positive in the areas to the northeast (17 nstrain/a) and negative (-29 nstrain/a) farther west along the subduction zone. This combination of positive and negative dilatation along the subduction zone is probably responsible for the lack of a more significant correlation between b and dilatation. •The change of dilatation from positive to negative as one goes east to west along the subduction zone suggests a transition in plate interaction from transtensional to transpressive. •Over the full range: Variations of b value correlate negatively with shear (r = -0.83, p = 0.04) in the zones of this subdivision. The correlation of b to dilatation is weakly positive (r = 0.73, p = 0.1). Correlation between seismicity and GPS strain