Yongxian Zhang, Xiangchu Yin & Keyin Peng C enter for A nalysis and P rediction( CAP ),

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