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(A)(B)(C)(D)▲▲Figure 10. The coseismic Δσ f caused by the mainshock with the two-segment slip model at different depths, with μ′ = 0.4. A), B),C), and D) show results for depths of 2 km, 5 km, 10 km, and 15 km, respectively. The strike angle, dip angle, and rake angle of receiverfault are 52°, 61°, and 128°, respectively. The beach balls show the location and mechanism of the mainshock and M w 6.3 aftershock.TABLE 2Δσ f at the 2011 Christchurch earthquake epicenter, caused by different mainshock models with three µ ′ values at four focaldepths. The focal mechanism of the receiving fault is 52°/61°/128°.µ′2 km 5 km 10 km 15 kmUniform fault plane model 0.0 0.062 0.062 0.066 0.0810.4 0.010 0.013 0.021 0.0360.8 –0.042 –0.036 –0.023 –0.008Two-segment slip model 0.0 0.087 0.095 0.113 0.1430.4 0.035 0.044 0.065 0.0940.8 –0.018 –0.008 0.017 0.044Stochastic model with single 0.0 0.110 0.143 0.183 0.214plane based on NEIC solution 0.4 0.004 0.033 0.086 0.1310.8 –0.103 –0.077 –0.010 0.048Stochastic model with foursegmentsDepth0.0 0.120 0.119 0.114 0.1210.4 0.048 0.053 0.058 0.0680.8 –0.023 –0.013 0.002 0.015810 Seismological Research Letters Volume 82, Number 6 November/December 2011
(A)(B)(C)(D)▲▲Figure 11. The coseismic Δσ f caused by the two-segment slip model at a focal depth of 5 km with μ′=0.4 for variations in receiverfault strike. A), B), C), and D) show results for strikes of 352°, 22°, 82°, and 112°, respectively. The dip and rake of the receiver fault areheld constant at 61° and 128°, respectively, in these calculations. The beach balls show the location and mechanism of the mainshockand M w 6.3 aftershock.at different focal depths with three values of apparent coefficientof friction. We find that different slip models can result insignificant differences in the amplitude and distribution of Δσ fin the near field of the fault, but no substantial difference inthe far field. On the other hand, focal depth and receiving faultgeometry play a much stronger role on Δσ f outside the immediatemainshock rupture zone. In our calculations for the 2011Christchurch earthquake, Δσ f can increase significantly (by afactor of 3) when the aftershock focal depth increases from 2 kmto 15 km. Additionally, our results show a change of 30 degreesin receiving fault geometry can even cause polarity changes inΔσ f . We also find the resulting Δσ f at the epicenter of the 2011Christchurch earthquake decreases significantly as the value ofapparent coefficient of friction (μ′) increases. This emphasizesthe need for careful consideration of the appropriate value ofμ′ for different faulting environments. It should be noted thatin this study we assume that the coseismic slip distribution ofthe Canterbury mainshock is responsible for the triggering ofthe Christchurch earthquake. Because the GPS measurementsafter the Canterbury earthquake show very little postseismicmotion (less than ~2% of coseismic) (Reyners 2011, this issue),postseismic deformation probably can be neglected. Howeverwe still cannot rule out the possibility that smaller aftershockstriggered the Christchurch earthquake as a secondary aftershockwith larger magnitude (e.g., Felzer et al. 2002).In general, we find the occurrence of the Canterburyearthquake with a reasonable set of parameter choices raisesthe Δσ f on the Christchurch fault plane beyond the 0.01MPa threshold, promoting the aftershock plane to break. Toimprove the accuracy of Δσ f analysis, and hence the probabilityassessment of aftershocks, it is helpful to carefully studysource parameters of historical earthquakes for each region tounderstand the potential receiving fault geometry. For M > 5.5earthquakes, the teleCAP technique used in this paper showspromise for obtaining accurate focal mechanism and depth.For M ~ 5 earthquakes not recorded with local broadbandseismic stations, teleseismic P waves are typically above noiselevel in the short-period band (~1Hz), and teleCAP can beSeismological Research Letters Volume 82, Number 6 November/December 2011 811
- Page 7: News and Notes (continued)Nominatio
- Page 11: Preface to the Focused Issue on the
- Page 14 and 15: TABLE 1Peak ground acceleration (PG
- Page 16 and 17: ▲▲Figure 2. A) Sketch of the
- Page 18 and 19: ▲▲Figure 4. A) Adopted moment r
- Page 20 and 21: ▲▲Figure 7. As in Figure 6 but
- Page 22 and 23: ▲ ▲ Figure 8. Misfit parameters
- Page 24 and 25: ▲ ▲ Figure 10. Spatial variabil
- Page 26 and 27: ▲ ▲ Figure 12. Standard spectra
- Page 28 and 29: Quigley, M., R. Van Dissen, P. Vill
- Page 30 and 31: slip on a 59-degree striking fault
- Page 32 and 33: ▲▲Figure 4. Convergence of inve
- Page 34 and 35: observations and other source studi
- Page 36 and 37: -42. 5-43. 0-43. 5-44. 0-44. 5-43.2
- Page 38 and 39: “Product CSK © ASI, (ItalianSpac
- Page 40 and 41: TABLE 2Solutions for fault location
- Page 42 and 43: -43.45(A)degrees N-43.50-43.552.52.
- Page 44 and 45: is still a good fit to the horizont
- Page 46 and 47: Coulomb Stress Change Sensitivity d
- Page 48 and 49: mation takes on a larger strike-sli
- Page 50 and 51: P 9.4267BLDU45P 20.1213CASY39P 2.62
- Page 52 and 53: ERMJNUMAJOINUJHJ2CBIJMIDWJOWYHNBTPU
- Page 54 and 55: (A)6.146.13(B)6.246.36Misfit6.156.1
- Page 58 and 59: (A)(B)(C)(D)▲▲Figure 12. The co
- Page 60 and 61: Luo, Y., Y. Tan, S. Wei, D. Helmber
- Page 62 and 63: −44˚00' −43˚00'4-Sep-2010Mw 7
- Page 64 and 65: TABLE 1Pairs of SAR imagery used in
- Page 67 and 68: Depth (km)Coulomb Stress Change(bar
- Page 69 and 70: Crippen, R. E. (1992). Measurement
- Page 71 and 72: AlpineFaultHope Fault38 mm/yr0+ +-1
- Page 73 and 74: σ 1dσ 3Nuσ 3CM w 7.1dw 6.2u70°M
- Page 75 and 76: Right-lateral Faults(A) Range Front
- Page 77 and 78: DISCUSSIONThe 2010-2011 Canterbury
- Page 79 and 80: Large Apparent Stresses from the Ca
- Page 81 and 82: ▲ ▲ Figure 2. Observed vs. pred
- Page 83 and 84: 10Obs SA(1s)AS1AS+SDAB 2006AB+SDSA(
- Page 85 and 86: Fine-scale Relocation of Aftershock
- Page 87 and 88: −43.25°OXZ0 10 20km−43.5°−4
- Page 89 and 90: A’0 km 4 8−43.5°B’B−43.6°
- Page 91 and 92: REFERENCESAvery, H. R., J. B. Berri
- Page 93 and 94: ▲ ▲ Figure 2. A) shows three-co
- Page 95 and 96: ▲ ▲ Figure 4. Vertical accelera
- Page 97 and 98: 0.8PRPC Z0.40Normalized (Max PGA +
- Page 99 and 100: Near-source Strong Ground MotionsOb
- Page 101 and 102: (A)Magnitude, M w876542009 NZdataba
- Page 103 and 104: Scale0.5 g5 seconds▲▲Figure 4.
- Page 105 and 106: (A)(B)Spectral Acc, Sa (g)North/Wes
(A)(B)(C)(D)▲▲Figure 10. The coseismic Δσ f caused by the mainshock with the two-segment slip model at different depths, with μ′ = 0.4. A), B),C), and D) show results for depths of 2 km, 5 km, 10 km, and 15 km, respectively. The strike angle, dip angle, and rake angle of receiverfault are 52°, 61°, and 128°, respectively. The beach balls show the location and mechanism of the mainshock and M w 6.3 aftershock.TABLE 2Δσ f at the 2011 Christchurch earthquake epicenter, caused by different mainshock models with three µ ′ values at four focaldepths. The focal mechanism of the receiving fault is 52°/61°/128°.µ′2 km 5 km 10 km 15 kmUniform fault plane model 0.0 0.062 0.062 0.066 0.0810.4 0.010 0.013 0.021 0.0360.8 –0.042 –0.036 –0.023 –0.008Two-segment slip model 0.0 0.087 0.095 0.113 0.1430.4 0.035 0.044 0.065 0.0940.8 –0.018 –0.008 0.017 0.044Stochastic model with single 0.0 0.110 0.143 0.183 0.214plane based on NEIC solution 0.4 0.004 0.033 0.086 0.1310.8 –0.103 –0.077 –0.010 0.048Stochastic model with foursegmentsDepth0.0 0.120 0.119 0.114 0.1210.4 0.048 0.053 0.058 0.0680.8 –0.023 –0.013 0.002 0.015810 Seismological Research Letters Volume 82, Number 6 November/December 2011
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