Yih-Min Wu
Dept. of Geosciences, National Taiwan University

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

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

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.

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.

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。

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

Regional Warning v.s. Onsite Warning
Early Warning Time of the Earthquake
of Sep. 20, 1999 (Mw7.6)
400
PGA
M w
6.6, focal depth 10 km
Knet Station NIG018
Epicentral distance 14 km
200
25
Blind zone of on-site warning
24
23
22
0 sec
10 sec
20 sec
30 sec
Warning time
0
-200
20
10
0
-10
-20
8
4
0
-4
-8
-12
0.5 cm
 c
Pd
Pd threshold warning
PGV
PGD
-3 0 3 6 9 12 15
Time after P arrival (second)
18 21
VSN no warning area
119 120 121
Longitude (E)
122

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).

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

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

(Espinosa-Aranda et al.
, 1995)

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).

-25
-50
-75
-100
75
50
25
0
1000
750
500
250
0
-250
-500
-750
-1000
100
100
75
50
25
0
-25
-50
-75
-100
09/20/1999 17:47 Mw 7.6
T d T pr
Sun Moon Lake
( = 9 km)
P arrival
S arrival
P arrival
S arrival
T w
< 0
T w
> 0
P arrival
Reporting time
S arrival
Taichung
( = 35 km)
Taipei
( = 145 km)
0 10 20 30 40
Time (sec)
50 60 70

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).

Nakamura (2009)

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)

Doi (2009)

Doi (2009)

Doi (2009)

Motivation in Taiwan

Using the telemetered signals from strong-motion instruments.
Since 2000
Virtual Sub-Network Approach
(VSN)
M
L10
Wu et al., BSSA, 1998; Wu and Teng, BSSA, 2002.

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

Virtual sub-network approach

Performances for VSN
0.28
~17 sec
28

Expected Early Warning Time of the
Earthquake of Sep. 20, 1999 (Mw7.6)
25
24
0 sec
23
10 sec
20 sec
30 sec
22
Warning time
119 120
VSN no warning area
121
Longitude (E)
122

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

τ c
& P d
Methods
τ c average period parameter of the initial three seconds P waves
– For magnitude determination
P d
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)

400
200
PGA
M w
6.6, focal depth 10 km
Knet Station NIG018
Epicentral distance 14 km
0
-200
-8
-12
0
-4
-20
8
4
20
10
0
-10
0.5 cm
-3
 c
Pd
PGV
Pd threshold warning PGD
0 3 6 9 12 15
Time after P arrival (second)
18 21

0.5
0
Station Code
Depth
HKD112
42 km
 c measured
 c
4.4s, Mw8.3
Epicentral
Distance
71 km
-0.5
2
TCU079
8 km
 c
3.8s, Mw7.6
8 km
0
-2
1
MYG011
42 km
 c
3.2s, Mw7.2
70 km
0
-1
4
TTR007
11 km
 c
2.4s, Mw6.7
13 km
0
-4
1
13 km
NIG020
9 km
 c
1.3s, Mw6.1
0
-1
0 3 6
Time (sec)
9
Japan
Taiwan
Japan
Japan
Japan
12

r


0
 
0

W
W
2
( )
2
( )

4

2


 


2 ˆ 2 f u f df u f
2 df

4

2 f
2

C

1 f
2

2
 r

Earthquake size could be determined by τ c
!

10
Taiwan 11 events
Southern California 26 events
Japan 17 events
1
0.1
4 5 log (
 c
) = 0.296 M w
- 1.716
Sdv=0.122, R=0.933
6
M w
7 8

Pd large than 0.5 cm following shakings may cause damage

100
No damage records (168)
No damage events average (21)
Damage records (40)
Damage events average (5)
10
4 cm
1
Chi-Chi
0.1
0.01
0.5 cm
0.1
1
Pd, Displacement (cm)
10

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

100
Taiwan 507 records
Southern California 199 records
Japan 74 records
10
1
0.1
0.001
0.01
Linear regression over 780 records log(PGV)=0.920 log(Pd) + 1.642
SDV = 0.326
0.1
Pd (cm)
1 10

τ c
& Pd for damaging event identification!

10
1
1998
Reuyli
1999
Chiayi
1994
Nanoa
2003
Chengkung
Damage
No Damage
1999
Chi-Chi
0.1
0.01
5 6
Mw
No damage records (168)
No damage events average (21)
Damage records (40)
Damage events average (5)
7 8

Warning could be given within one second after P arrival!

1
0
-2
-4
2
2
0
6
4
-1
-2
2007/03/25 Noto Mw6.7 earthquake
ISK006

=7 km
ISK005

=19 km
-2 -1 0 1 2
Time after P arrival (sec)
3 4

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.

An examination using building array records from a damage building

2
1.5
1
0.5
0
0.1
Ch03: Free-field
Ch11: F1
Ch18: RF
Ch21: RF
Ch22: RF
Taitung EQ
Pd=0.5 cm
Chi-Chi EQ
Chengkung EQ
1
PGV (cm/s)
10

uncontrolled controlled h
K
Kanamori (2005)


0.5 g

8 feet controlled
Kanamori (2005)

Nakamura (2009)

Doi (2009)

Takamatsu (2009)

Takamatsu (2009)

Takamatsu (2009)

Takamatsu (2009)

Takamatsu (2009)

Motosaka (2009)

Motosaka (2009)

Motosaka (2009)

Motosaka (2009)

Sugano (2009)

Sugano (2009)

Sugano (2009)

Sugano (2009)

Sugano (2009)

Human Sensor

Thanks to
Profs. Ta-Liang Teng (USC), Willie H. K. Lee
(USGS), Yi-Ben Tsai (PG&E), Tzay-Chyn Shin
(CWB), Richard Allen (UC Berkeley)
Drs. Nai-Chi Hsiao (CWB), Chien-Hsin Chang
(CWB), Chien-Fu Wu (CWB), Li Zhao (IES),
Yamada Masumi (Kyoto Univ.), Barry Hirshorn
(PWTC)
Mrs. Da-Yi Chen (CWB), Jang-Tian Shieh (NTU)
Central Weather Bureau, Taiwan
NIED, Japan
SCEC, USA