Development of Earthquake Early Warning in Taiwan

1. Development of Earthquake Early Warning Yih-Min Wu Dept. of Geosciences, National Taiwan University

3. 如何降低地震災害？ • 長期 • 土地利用規劃 • 中期 • 耐震設計 • 短期 • 地震預測 • 地震發生

4. Earthquake Early Waning • Before Occurrence • Earthquake Prediction – Predicts Earthquake • Before Strong Ground motion • Seismic Early Waning System (EWS) • Predicts Shaking • Before Damage is Discovered • Seismic Rapid Reporting System (RRS) • Predicts Damage • Focusing seismic rescue efforts

5. Philosophy • Currently precise prediction of earthquake process is difficult. • However, once seismic waves are excited, the process is governed by known “Elasticity theory” and “Earth structure”, and the behavior is more predictable, and we can respond to ever-changing situation associated with an earthquake and its aftermath.

6. Environment is Changing • Large cities, high-rise buildings, bridges, tunnels, airport, gas, telephone, electricity, etc. • But, developments in modern engineering (e.g., structural control) will allow effective use of rapid seismic information to mitigate seismic hazards.

7. 地震預警應用範圍 • 學校學童躲入桌子底下尋求保護及心理應變。墨西哥市的預警系統研究成果顯示，接受地震預警訊息的學童，在心理上大幅降低對地震之恐懼。 • 工人能離開危險的工作位置。 • 醫院進行的手術能暫時停止或調整精細及關鍵的操作，例如:眼科手術等。 • 運輸系統能自動停止或減速，例如:高速鐵路列車減速以降低翻車之風險。 • 維生管線及通訊網路能自動調整、重組或關閉，例如:關閉瓦斯及供水管線，減少地震所引起之火災及其他災害。 • 工廠能及時進行緊急應變，保護振動敏感之設備，例如:晶元製造廠。

9. Earthquake early warning (EEW) • Before Strong Ground Motion • Earthquake Early Waning System • Predict Shaking • Regional Warning & Onsite Warning

10. Regional Warning v.s. Onsite Warning

11. Background • Cooper (1868) proposed EEW concept “arrange a very simple mechanical contrivance at various points from 10 to 100 miles from San Francisco” & “instantaneously ring an alarm bell… near the center of the city” • A hundred years later, Japan Railways designed an EEW system in 1965 and started to operate in 1966 (Nakamura, 1988).

12. A concept of the Regional warning Nakamura and Saita (2006)

13. The first successful case • The Mexico City Seismic Alert System successfully provided about 70 sec of advanced warning of the 14 September, 1995, Copala (Guerrero, Mexico) earthquake to the citizens of Mexico City (Espinosa-Aranda et al., 1995). • To public system

14. (Espinosa-Aranda et al., 1995)

15. Successful case in Taiwan • 102 sec after the 1999 Chi-Chi earthquake, the CWB of Taiwan reported the hypocenter, magnitude (M7.3), and shaking map to public (Wu et al, 2000). • In 2002, the CWB achieved 22 sec reporting time after the occurrence of an earthquake (Wu and Teng, 2002).

17. Successful case in Japan • Urgent Earthquake Detection and Alarm System (UrEDAS), this system worked during the Niigata Chutsu earthquake in 2004. It immediately detected the P-wave arrival and shut off the train’s power in less than 3 seconds after P arrival (Nakamura et al., 2006).

18. Nakamura (2009)

19. Big progress in Japan 2007 • JMA started official distribution of early warning information to a limited number of organizations in August, 2006, and plans to distribute it to the public in the fall of 2007. • System was successfully activated during the 2007 Noto Hanto and Niigata Chuetsu-Oki earthquakes, and provided accurate information regarding the source location, magnitude and intensity at about 3.8 s after the arrival of P wave at nearby stations. Odaka et al. (2003) & Kamigaichi (2004)

20. Doi (2009)

21. Doi (2009)

22. Doi (2009)

23. Motivation in Taiwan

25. EWS in Taiwan Using the telemetered signals from strong-motion instruments. Since 2000 Virtual Sub-Network Approach (VSN) ML10 Wu et al., BSSA, 1998; Wu and Teng, BSSA, 2002.

26. Real-time strong-motion network • Accelerometer- • 102 stations (20km averaged spacing) • 16 bits resolution • ± 2g Max. amplitude • Telemetry - • Real-time data stream (RTD) • 4.8K dedicated telephone line • Sampling rate 50 sps • 0.2 sec averaged delay • Data processing - • Taipei data center • Windows-based workstation

27. Virtual sub-network approach

28. Performances for VSN 0.28 ~17 sec 28

31. For onsite case, an earthquake occurs, you may think about • Large earthquake? • Cause damage? • Is this place safe?

32. τc & Pd Methods • τcaverage period parameter of the initial three seconds P waves • For magnitude determination • Pd 0.075Hz high pass peak displacement amplitude of the initial three seconds P waves • For intensity estimation & damage identification Wu and Kanamori (2005a,b; 2008a,b)

36. Earthquake size could be determined by τc!

38. Pd large than 0.5 cm following shakings may cause damage

40. PGV could be predicted by Pd and then Shaking Intensity could be predicted!

42. τc & Pd for damaging event identification!

43. 2003 Chengkung 1999 Chi-Chi 1999 Chiayi 1998 Reuyli 1994 Nanoa

44. Warning could be given within one second after P arrival!

46. Combination with modern MEMS sensor. Cheaper device may install to every building to give warning within three seconds after P arrival after a large earthquake occurs.

47. An examination using building array records from a damage building