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Spatial & Temporal Variation of LURR in Southern California: Implications for Earthquake Tendency

This study examines the Load/Unload Response Ratio (LURR) in Southern California and its relationship to earthquake tendency in the region. It explores the calculation of LURR, variation before strong earthquakes, and earthquake catalog analysis. The findings provide insights for understanding California's fault system and earthquake predictions.

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Spatial & Temporal Variation of LURR in Southern California: Implications for Earthquake Tendency

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  1. Study on Spatial and Temporal Variation of LURR in Southern California and Its Implication to Earthquake Tendency in This Region Yongxian Zhang, Xiangchu Yin & Keyin Peng Center for Analysis and Prediction(CAP), China Seismological Bureau(CSB), Beijing 100036, China (e-mail: zhang.yongxian@263.net; phone 86-10-88015551; fax: 86-10-68218604). CAP, CSB

  2. Outline CAP, CSB • About LURR • Fault System in Southern California(SC) • Field Stress in SC • Calculation of Y/Yc • Variation of Y/Yc before Some Strong Earthquakes in SC • Earthquake Tendency in SC • Discussion

  3. LURR—Load/Unload Response Ratio Put forward by Prof. Xiangchu Yin in 1987 - Yin X.C.(1987), A new approach to earthquake prediction, Earthquake Research in China, 3,1-7(in Chinese with English abstract) Basis: The seismogenic process is nonlinear and irreversible so that the response to loading is different from that to unloading. Y=X+/X- X+-- response rate under loading condition X--- response rate under unloading condition Y--LURR

  4. How to calculate LURR? 1. Find a easy way to calculate LURR Where E denotes AE energy; “+” means loading “–” means unloading. m=1, Em is exactly the energy itself; m=1/2, Em denotes the Benioff strain; m=0, ∑Em denotes the number of events. --Xiang-Chu Yin, et al.(2000), Pure and applied Geophysics,157(2000), 2365-2383

  5. How to calculate LURR? 2. Criteria to Judge loading and unloading Loading--the rate of Coulomb failure stress is positive. Unloading-- the rate of Coulomb failure stress is negative. --Xiang-Chu Yin, et al.(2000), Pure and applied Geophysics,157(2000), 2365-2383 -normal stress -shear stress -coefficient of internal friction

  6. Obtaining high confident LURR? Y(LURR) is sensitive to the number of earthquakes, when Y is greater than the critical value(Yc), the confidence of Y Anomaly is higher. N Yc(90%) Yc(95%) Yc(99%) 20 3.18 4.17 7.69 21 3.09 4 7.21 22 2.98 3.83 6.59 …… 36 2.26 2.68 3.89 …… --Zhuang and Yin(1999), Earthquake research in China, 15(128-138). So we express the LURR by Y/Yc. When Y/Yc is greater than 1, the anomaly of LURR is confident.

  7. Outline CAP, CSB • About LURR • Fault System in Southern California(SC) • Field Stress in SC • Calculation of Y/Yc • Variation of Y/Yc before Some Strong Earthquakes in SC • Earthquake Tendency in SC • Discussion

  8. understanding of California's fault system. The 1994 Fault Activity Map of California and Adjacent Areas by Charles W. Jennings (available from the California ... www.scecdc.scec.org/faultmap.html

  9. CALIFORNIA SOUTHERN REGION dominated primarily by northwest-trending , generally of a right-lateral strike-slip nature

  10. CALIFORNIA NORTHWEST REGION, every kind of fault type can be found here.

  11. MOJAVE REGION, dominated by northwest-trending, right-lateral strike-slip faults

  12. BASIN AND RANGE REGION characterized by roughly north-south trending valleys and mountain ranges, bounded typically by normal faults

  13. NORTHWEST REGION dominantly a region of reverse faulting, but faults of every sort can be found on this map

  14. Outline CAP, CSB • About LURR • Fault System in Southern California(SC) • Field Stress in SC • Calculation of Y/Yc • Variation of Y/Yc before Some Strong Earthquakes in SC • Earthquake Tendency in SC • Discussion

  15. Tectonic Stress of America

  16. Outline CAP, CSB • About LURR • Fault System in Southern California(SC) • Field Stress in SC • Calculation of Y/Yc • Variation of Y/Yc before Strong Earthquakes in SC • Earthquake Tendency in SC • Discussion

  17. 1. Division of Southern California U X A2 V Z NC02 NC04 NC01 NC03 T W Q A1 R Y1 SC08 NC07 SC11 S P O SC09 SC05 M SC06 N K L SC04 SC03 C E I SC10 D SC01 J B H SC02 A F1 F G

  18. Determine the limit magnitude of earthquakes • Earthquake Catalogue: from CNSS

  19. SC01 ML: 2-3.5 Gutenberg-Richter relation

  20. Scaning parameters: • Temporal window: 12 months • Time moving step: 3 month • Spatial window: R=100km • Space moving window: • Nmin=20 R

  21. Outline CAP, CSB • About LURR • Fault System in Southern California(SC) • Field Stress in SC • Calculation of Y/Yc • Variation of Y/Yc before Some Strong Earthquakes in SC • Earthquake Tendency in SC • Discussion

  22. 1980-2001 M>=6.5 in California Loma Prieta Coalinga Hecter Mine Northridge Landers Superstition Hills

  23. For 1983-05-02 Coalinga 6.7 earthquake

  24. 1982-03

  25. 1982-06

  26. 1982-09

  27. 1982-12

  28. 1983-03

  29. For 1987-11-24 Superstition Hills 6.6 earthquake

  30. 1986-09

  31. 1986-12

  32. 1987-03

  33. 1987-06

  34. 1987-09

  35. For 1989-10-18 Loma Prieta 7.0 earthquake • California: An Interpretive History , • by James Rawls and Walton Bean, 7th edition (McGraw-Hill, 1998). • The Elusive Eden: A New History of California , • by Rice, Bullough, and Richard Orsi, 2nd edition (McGraw-Hill, 1996). • Geosystems: An Introduction to Physical Geography , • by Robert Christopherson, 3rd edition, (Prentice-Hall, 1997).

  36. 1988-09

  37. 1988-12

  38. 1989-03

  39. 1989-06

  40. 1989-09

  41. For 1992-6-28 Landers 7.3 earthquake

  42. 1991-09

  43. 1991-12

  44. 1992-03

  45. For 1994-1-17 Northridge 6.6 earthquake On January 17,1994 the most expensive earthquake in the United States, a 6.7, hit Southern California. It was caused by a deeply buried thrust fault 11 miles underground, beneath the San Fernando Valley.

  46. 1992-12

  47. 1993-03

  48. 1993-12

  49. For 1999-10-16 Hector Mine 7.1 earthquake

  50. 1999-03

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