CAP, CSB 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

Outline About LURR Fault System in Southern California(SC) 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

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

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

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

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.

Outline About LURR Fault System in Southern California(SC) 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

understanding of California's fault system 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

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

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

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

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

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

Outline About LURR Fault System in Southern California(SC) 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

Tectonic Stress of America

Outline About LURR Fault System in Southern California(SC) 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

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

Determine the limit magnitude of earthquakes Earthquake Catalogue: from CNSS

SC01 ML: 2-3.5 Gutenberg-Richter relation

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

Outline About LURR Fault System in Southern California(SC) 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

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

For 1983-05-02 Coalinga 6.7 earthquake

1982-03

1982-06

1982-09

1982-12

1983-03

For 1987-11-24 Superstition Hills 6.6 earthquake

1986-09

1986-12

1987-03

1987-06

1987-09

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).

1988-09

1988-12

1989-03

1989-06

1989-09

For 1992-6-28 Landers 7.3 earthquake

1991-09

1991-12

1992-03

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.

1992-12

1993-03

1993-12

For 1999-10-16 Hector Mine 7.1 earthquake

1999-03

1999-06

1999-09

Remarks Future earthquake located near region of anomalous Y/Yc. Date Epicenter Magnitude/ (km) Max Y/Yc Lasting Time of anomalous Y/Yc 1983.5.2 Coalinga 6.7/? ? 1987.11.24 Superstition Hills 6.6/0 1.4 21m 1989.10.18 Loma Prieta 7.0/100 1.2 24m 1992.6.28 Landers 7.3/100 1.0 18m 1994.1.17 Northridge 6.6/80 25m 1999.10.16 Hector Mine 7.1/100 15m Remarks Future earthquake located near region of anomalous Y/Yc. Anomalous Y/Yc lasts about 1-2 years before upcoming earthquake.

Outline About LURR Fault System in Southern California(SC) 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

Earthquake Tendency in Southern California There might be moderate earthquake about 5 around (36N, 119W) and (36N, 121.6W) within about 1 year. The results also show that there are no LURR anomalies in other regions, which implicates that there is less strong earthquake hazard in Southern California in the near future.

Outline About LURR Fault System in Southern California(SC) 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

Discussion LURR is a promising approach to mid-term earthquake prediction. However, calculation of LURR depends on high quality earthquake catalogue and other data. Up to now, we can not give an exact earthquake prediction by LURR, but an approximate one. For earthquakes greater than 6.5 in Southern California, the size of anomalous LURR are among 100-300km, which might imply the seismogenic region size. In addition, evolution of anomalous LURR is complex.

Acknowledgements QUAKES NSFC(Grant 19732060, 40004002) CNSS, SCEC

SC02 ML: 2-4.0

SC03 ML: 2-4.0

SC04 ML: 2-3.5

SC05 ML: 2-3.5

SC06 ML: 2-4.0

SC07 ML: 2-4.0

SC08 ML: 2-4.0

SC09 ML: 2-3.5

SC10 ML: 2-3.5

SC11 ML: 2-3.5

1995.10.6 Tangshan 4.9

1997.5.25 zhangjiakou Ml:4.7

1997.9-1998.8 1999.3.11 zhangbei 5.6

1997.10-1998.9 1999.3.11 zhangbei 5.6

1998.5-1998.10 1999.3.11 zhangbei 5.6

1997.6-1998.11 1999.3.11 zhangbei 5.6

1998.7-1998.12 1999.3.11 zhangbei 5.6

1998.8-1999.1 1999.3.11 zhangbei 5.6

1998.9-1999.2 1999.3.11 zhangbei 5.6

1998.10-1999.3 1999.5.15 hunyuan Ml:4.6

1998.11-1999.4 1999.5.15 hunyuan Ml:4.6

1998.12-1999.5 1999.5.15 hunyuan Ml:4.6

considering the influence of random factors on LURR.