8CUEE CONFERENCE PROCEEDINGS
8th International Conference on Urban Earthquake Engineering
March 7-8, 2011, Tokyo Institute of Technology, Tokyo, JapanON THE EFFECTIVE EARTHQUAKE EARLY WARNING SYSTEMSFOR BOTH DISTANT AND NEAR EVENTS

Yutaka Nakamura1), 2)
1) President, System and Data Research, Tokyo, JAPAN2) Visiting Professor, Dept. of , Tokyo Institute of Technology, Yokohama, JAPANyutaka@sdr.co.jp

Abstract: This paper describes the truly effective early warning systems with simulated results for disaster prevention
against distant and near events. And the role of national or public organizations in earthquake disaster prevention will be
discussed.

1. INTRODUCTION
It is clear that the basic countermeasure against
earthquake strong motion is to reinforce buildings and otherstructures. However, even enough counter-measured
facilities against expected strong motion un-expecting
accidents may be occurred. Against the un-expecting
accidents, the earthquake early warning system, UrEDAS,
Urgent Earthquake and Detection and Alarm System, wasdeveloped 25 years ago. At first the system was adopted for
the Seikan under-sea-tunnel as an earthquake information
system in 1988, and then fully operated for safety of theTokaido Shinkansen from 1992. After that we aredeveloping and improving our systems on the experiences of
the Kobe earthquake and etc., as the technical innovationgroup for the EEW, Earthquake Early Warning. As theresults of our activities, FREQL, Fast Response Equipment
against Quake Load, was developed. At the start of the
UrEDAS operation, the processing time of warning wasthree seconds after the P-wave detection. Now theprocessing time of FREQL is shortened to 0.1 second inminimum. This shortened processing time makes possible toissue a quick alarm over one second leading for large motion
against even an under earthquake. Although this time margin
is very short, it is expected that significant effects will be
generated for facilities operated under the ultimate situation
as the bullet train or the elevator system of high-risebuildings. The ultimate EEW system as FREQL is useful for
rescue activities just after the earthquake damage to preventthe second disaster by large aftershocks.
In 1992 Nakamura’s Group of RTRI, Railway
Technical Research Institute, proposed a project of UrEDAS
network with 2000 stations not only for earthquake disasterprevention, but also for working as a node ofcommunication network when natural disaster occurred. In
1992, TV news of NHK, Nihon Hoso Kyoukai (Japan

Broadcasting Corporation) announced that a trial operationof EEW information service for Tokyo metropolitan areawith UrEDAS information will start in 1993. But this project
was not realized mainly because of objection of JMA, Japan
Metrological Agency. JMA started the similar project in2005 using a system developed by themselves. In this paper,
not only the EEW of Japan, but also the present state of theinformation for earthquake disaster prevention will be
described.
2.

CONCEPT OF EEW

There are two kinds of earthquake alarms as illustrated
in Figure 1. One is the “On-Site Alarm” which is an alarm
based on observations close to the objects to be warned.
The other one is the “Front Alarm” which is an alarm basedon observations near the epicentral area, which is then used
for the warning in possible damage areas away from theepicenter. Because the latter alarm concept requires the useof communication networks, it is also sometimes called
On--SiteOn
Detection/Alarm
Front
Detection/AlarmP
P-wave Alarm

S-wave Alarm

S

Fault Rupture

Figure 1 Concept of an EEW system

No Damage

Possible Damage Area
Possible Damage Area
for magnitude M
for magnitude M

Damages for Embankments?
Δ

Damages for Bridge

100

Epicenter

al
20G

10

l
Ga
40

1
3

4

Δ

Gal

The idea of disaster mitigation by the EEW depends on
the progress of science and technology during 19 and 20
centuries. Earthquake is a vibration caused by the results ofthe crust destruction. Although the earthquake prediction
obviously brings numerous benefits to the disasterprevention, this kind of destructive phenomena is astochastic phenomenon and is impossible to predict its
occurrence with enough accuracy and reliability applicable
to disaster prevention. Instead of the prediction the EEW isclose up for disaster prevention.
The idea to minimize the direct effects of earthquakes
by developing an early warning system was first publishedby Dr. J. D. Cooper (1868) with the aim of earthquake
disaster prevention in San Francisco. It is interesting for methat he describes the idea of EEW based on the failure of theJapanese earthquake prediction method using a magnet at an
earthquake in 1868. After Cooper various similar ideas has
been proposed, but Cooper’s and the other ideas were neverrealized and then basically forgotten.
About 100 years after Dr. Cooper’s publishing,
independently a similar idea was born from an idle talk at a
tea time of an university laboratory. This is the detection
system before 10 seconds for Tokyo metropolitan area
proposed by Dr. Hakuno et al (1972). At the same time,
many institutions and agencies including JMA started toresearch a possible EEW based on the existing automatic
earthquake observation system consisting of a network ofmany monitoring stations.
JNR, Japanese National Railways, had also started toresearch possible EEW based on the same concept as JMA,
while Nakamura at the RTRI of JNR, started to develop a
different concept in 1979, using only a single station. He
completed the prototype UrEDAS, pronounced “Yuredasu”
meaning “shaking begins” in Japanese. This was the first
actual P-wave detection and alarm system worldwide andwas published in Nakamura (1984).
The main UrEDAS functions are the estimation ofmagnitude and location, vulnerability assessment andissuing warnings within a few seconds using initial P-wave
motion at a single station. Unlike other automatic seismic
observation systems, UrEDAS does not have to transmit theobserved waveform in realtime to a remote processing or
centralized system and is therefore comparatively simple.
UrEDAS calculates parameters such as back azimuth,
predominant frequency for magnitude evaluation andvertical to horizontal ratio for discrimination between P and
S waves, using the amplitude for each sample in realtime.
These calculations are processed in realtime without storing
waveform data. The amount of processing of UrEDAS is

120

UrEDAS

8 0G
al

3.

almost constant regardless of whether or not an earthquake isoccurring, so the number of computational processes does
not increase in the event of an earthquake. Then UrEDAS
does not cause any system down after big earthquake.
UrEDAS can issue its alarm based on the M-Δ diagramin Figure 2 immediately after the earthquake detection.
The M-Δ diagram is derived from past damage experience to
JNR facilities and equipment and aids in decreasing thenumber of false or needless alarms. This kind of alarm isreferred to as the M-Δ Alarm. UrEDAS can also assist indecisions to safely restart train operations based on thedetailed earthquake parameters.

Epicentral Distance in km“Network Alarm”. Both alarm types described can make useof two different triggers, also called “alarms”. One is thetrigger/alarm exceeding a preset level, the so-called “S-wave
Alarm” or “Triggered Alarm”; the other one is thetrigger/alarm during the preliminary motion, the so-called“P-wave Alarm”.

5

6

M 7

8

Magnitude M

Figure 2 M-Δ diagram
After an initial testing period, the development of
UrEDAS for routine use was completed and trial operations
for the protection of the Shinkansen line, the bullet train, in
central Japan were carried out commencing in 1990. These
trials led to the implementation of some additional
capabilities and functionality of UrEDAS. In 1992, UrEDAS
started routine operations with full functionality for theTokaido Shinkansen line (Nakamura, 1996). These UrEDAS
issue a P-wave warning with a processing time of just threeseconds after detecting the P-wave.
Other organizations, such as JMA, continued theirresearch and development but without implementing
operational systems. This made JNR the only agency toimplement an operational and functioning actual warning
system in the 20th Century.

4.

THE 1995 KOBE EARTHQUAKE AND Compact
UrEDAS

After the 1995 Kobe earthquake, it was recognized thatan even shorter warning time would lead to even more
effective realtime disaster mitigation. To achieve this,
UrEDAS was developed further with the aim of being able
to issue warnings within about one second after the detectionof a damaging earthquake. The resulting system was theCompact UrEDAS which became available in 1997
(Nakamura, 1998) and commenced routine operations for
the Tohoku, Joetsu and Nagano Shinkansen lines in 1998.
In contrast to UrEDAS which estimates thedestructiveness of the earthquake from the earthquake’s
parameters, Compact UrEDAS derives this from theearthquake motion directly ‘in realtime’ and then issues thealarm, if required. To estimate earthquake dangerousness,the power density PD (W/kg) of the earthquake vibration is
calculated from the inner product of the acceleration vector a(cm/s2) and the velocity vector v (cm/s). As this value is alarge number, it is normally expressed in terms of the
Destructive Intensity (DI) defined as the logarithm ofabsolute value of this inner product (LPD, logarithm of thepower density) as Eq. (1). The concept of DI is illustrated in
Figure 3.

Acceleration in Gal_ EW

100
50
0
-50
-100

NS

Z

The Change of RI and Acceleration observed at the 2003 Miyagiken-Oki Eq. M7.0

E = mv2/2
= ma
ma
FF =

F= ma
m

v

PW = mavFv （（（PW = F∙v = ma∙v
DI = log10 |a∙v|

with cgs unit

PD = PW/m = a∙v
LPD = log10 |a∙v|

with MKS unit

Figure 4 Time history of relevant earthquake

RI = DI + 2.4 = LPD + 6.4
MMI = (11/7)∙RI + 0.5
Figure 3 Relationship between various earthquake
DI = log |a·v| = LPD + 4.0(1)

The maximum value of DI during an event, DImax
relates to the earthquake damage and is similar to the
instrumental intensity scale of JMA, IJMA, with the constantdifference of 2.4, and corresponds to MMI, the Modified
Mercalli Intensity. These indices are referred as RI, Realtime
Intensity, and MMI, respectively.
RI = DI + 2.4
MMI = (11/7)RI + 0.5 = (11/7)DI + 4.27

(2)
(3)

IJMA can only be calculated after earthquake terminationaccording to its artificial definition without physicalbackground. Contrary to this, DI is defined as the logarithmof Power Density multiplied by a constant. Power Density isa physical variable related closely to earthquake damage. DI
can be calculated in realtime and its value increases
immediately after the P-wave arrival. Because DI is sensitive
to the P-wave arrival, it can be used to define a P-wave
alarm. Figure 4 shows the change of RI as a function of timewith the acceleration waveform and the change of SI,
Spectral Intensity. RI is more sensitive than both, theacceleration and SI, because the value of RI increases
drastically at the P-wave detection, about one second prior tothe other indices.
When the P-wave arrives, RI increases dramatically,followed by a further but slower increase until the arrival of
the S-wave, by which time it reaches its maximum, called
RImax. The PI-value is defined as the maximum RI within t
seconds after P-wave detection. This PI-value seems to be
applicable as a trigger for the P-wave alarm. Furthermore, it
is possible to estimate RImax from the PI-value approximately.

Because each facility has its own withstanding intensity
level, each customer can determine the PI-value as thetrigger of the P-wave alarm. In other words, with thecontinuous observations of RI, an earthquake alarm can beissued efficiently and the damage can be estimated reliably.
In fact, the PI-value with its physical meaning of power
related to destructiveness and dangerousness of theearthquake can thus be used for a P-wave alarm as realized
in the Compact UrEDAS and FREQL (explained later indetail).
The function of the Compact UrEDAS is to issue anearly warning for the area close to the instrument based on
the risk of the detected earthquake motion, which is different
from the alarm from the UrEDAS to the area of possible
damage based on the estimated location and magnitude ofthe detected earthquake. The target area of the UrEDAS
alarm is about 200 km around the location of the instrument,
while that of the Compact UrEDAS alarm is only about
20km around the instrument. Thus, to maximize theeffectiveness of the warning system, an ideal strategy is to
use the UrEDAS (front alarm or network alarm) to respondto more distant large earthquakes and use the Compact
UrEDAS (on-site alarm) to respond to nearby earthquakes.

5.

EXAMPLE OF A SUCCESSFUL EEW BY
Compact UrEDAS

The derailment of one Shinkansen train during the2004 Niigata-ken Chuetsu Earthquake (M6.8) impressively
demonstrated the effectiveness and benefits of the early
warning system for Shinkansen train operations. The factthat there were no fatalities or injuries to the passengers andcrew of the train is clearly a result of the availability of theearly warning system. The circumstances and course of
events of the derailment are described in the following.
Figure 5 shows a summary and timeline of the events.
The train line is built on many viaducts, and two ofthem with different characteristics are joined at 300m from

Figure 5 The Shinkansen Derailment during the 2004 Niigata-Ken Chuetsu Earthquake
the tunnel exit including the snow-shade (the 300m point
hereafter). The earthquake effects on these viaducts weredifferent from each other. When the train passed the 300m
point, it is likely that the train derailed, because the joints in
the rail tracks underwent different displacements.
The power supply to the train was interrupted by the
P-wave alarm of the Compact UrEDAS installed at thesubstation (SS), 11km from the epicenter of the earthquake.
The alarm was triggered about 2.5 seconds before the arrivalof the S-wave at the location of the train. The large motion
started one more second after that. So the P-wave alarm
preceded the onset of the large motion by about 3.5 seconds.
Without the automatically initiated emergency breaking
triggered by the alarm the train would have arrived at the
300m point earlier and more vehicles would have passed
that point during the large motion. With the very realpossibility of the rails buckling while the train passed overthem at great speed, this most probably would have caused amuch more serious derailment destroying the rails
completely which then might well have led to the train
overturning.
If this happened to the lead vehicles, it could havebeen as catastrophic as the accident of the German ICE(InterCity Express) high-speed train in 1998 (Wikipedia).
Consequently, although the derailment could not be
prevented, this certainly illustrates the usefulness of thewarning system impressively.
A subsequent simulation of the alarm behavior of a
FREQL system using the recorded waveform showed thatthe train would have received the P-wave alarm another 0.8
seconds earlier, if a FREQL had been installed in

Shin-Kawaguchi SS, because the FREQL would have issued
the P-wave alarm already 0.2 seconds after the P-wave
detection.
There are several more examples of successful
warnings by UrEDAS or Compact UrEDAS in 1995, 2003,
2005 and as detailed in Nakamura and Saita (2007).

6.

JMA’S EEWIn about the Year 2000, JMA started research on asingle site detection system with the Railway TechnicalResearch Institute. Their system concept was basicallysimilar to the ideas behind the UrEDAS. However, incontrast to the UrEDAS which is a direct realtime system,
the JMA development adopted an intermittent processing
system by determining the necessary parameters using
stored waveform data of several seconds duration to fit theestimated function. As such, JMA’s centralized systemgathered information of each site and re-processed it using
the stored information from many sites, and then issued an
alarm, if necessary.
Therefore, JMA’s EEW can be regarded as a
network-type alarm system that requires a normallyfunctioning telecommunications network. Except for thecases of extremely deep earthquake events, the combinationof processing time and telecommunication time (the time ittakes for the observations to reach the central system) is toolong to issue a meaningful alarm for the possible epicentral
damaged area before the large earthquake motion from anearby earthquake or an epicentral earthquake starts.

Therefore, this system is unable to issue a warning before
the onset of the large earthquake motion at the damaged area.
In some cases, the warning was even issued after terminationof the earthquake motion. In the case of the 2008
Iwate-Miyagi-Nairiku Earthquake, for instance, it was
impossible for the system to issue the warning for thedamaged area.

7.

ULTIMATE EEW SYSTEM: FREQL

The functions of UrEDAS and Compact UrEDAS werecombined which not only reduced the size and weight of thesystem, but also improved its functionality. Thisdevelopment was completed in 2005 and given the name
FREQL. In Japanese, FREQL, pronounced “furekkuru”,
means “wave coming”. FREQL shortened the processing
time required to issue an UrEDAS /P-wave alarm - based on
the estimated earthquake parameters from three seconds (forUrEDAS) to one second. The previously minimum time for
issuing a P-wave alarm based on the dangerousness of thedetected earthquake motion by the Compact UrEDAS of one
second was improved by the FREQL to just 0.2 seconds andfurther to 0.1 seconds in 2009. This enables FREQL to issue
an alarm before a large earthquake motion even in the caseof the epicentral area.
FREQL is not only very valuable in the detection of theinitial quake, but is also used during rescue operations after
the main shock by detecting, and warning for possible
aftershocks. For instance, the Tokyo Fire Department Hyper
Rescue Team pulled out a small child from underneathdebris from a land slide during the 2004 Niigataken-Chuetsu
Earthquake. After that they had contacted us for using
FREQL to keep the safety of the rescue staff during the highrisk of aftershocks. Based on their request, a portable versionof the FREQL was developed in 2005, improving thesystem’s capabilities further and making it more compact.
The Hyper Rescue Team examined FREQL not tocause false alarm because of the working heavy equipments.
And also functional examination with the high quality three
dimensional shaking table made skeptic person understandthat FREQL should be useful for earthquake disasterprevention.
The portable FREQL is now in use by many fire

Figure 6

FREQL used by Japanese International
Rescue Team at the Sichuan Earthquake

Figure 7 Processing Time of the EEW systems
departments nationwide, even accompanying international
disaster rescue teams, such as to the 2006 Pakistan
Earthquake and the 2008 Sichuan Earthquake, see Figure 6.

Table 1 Comparison between SDR and JMA methods
MethodProducts

P, S-wave
Recognition

Processing
Magnitude M Epicentral Distance Δ
Time
from
from
Interval

UrEDAS
SDR

Compact UrEDAS
FREQL

Yes

1/100 s.

InitialPeriod *Initial Amplitude
and M(S-P Time after S) *

*

No?

1 s.

Amplitude
and Δ

except Compact UrEDAS .
corresponds to warning based on Initial RI / M-Δ, respectively.
RI : Realtime Seismic Intensity.

**

Alert Issueing
after Trigger

Development /Practical Use

M-Δ

Set to 3 s.

1984/1989～

Initial RI

Set to 1 s.

1997/1998～

Initial RI / M-Δ Min. 0.1 s./ 1s. * * 2003/2004～
Initial RI / M-Δ Min. 0.2 s./ 1s. * * 2007/2008～

AcCo-PS
JMA

Warning
based onInitial Gradient of
Amplitude

Estimated
SesmicIntensity

Average 5.4 s.
(Minimum 2 s.)

2004/2007～

earthquake damage.
The alarm processing time of EEW Systems explained
above is shown in Table 1 and Figure 7, is the comparisonof each EEW’s functions.
Tokyo Institute of Technology has started operation ofunique earthquake information system integrated with adisplay board. Normally this system shows general campus
information with recent earthquake observed information.
And if AcCo-PS, P-wave warning device with FREQL
function, detects an earthquake, this system shows
waveform and RI and PGA with frequency range between
0.1 Hz and 5 Hz (5HzPGA), see Figure 8.

8. SIMULATIONS OF FREQL ALARM
In this section simulated examples will be presented fordamaged earthquakes; big near event, near event and huge
distant event.

Figure 88.1. A Big Near Event
The 2008 Iwate-Miyagi-Nairiku Earthquake, M7.2 and
8 km depth, was occurred in north-east of Japan at 14th June
2008, around 8:43 of local time. This earthquake caused
severe damage in the epicentral area, yet JMA’s EEW
system was unable to issue an alarm before the start ofshaking in the damaged area within approximately 25 km of
the epicenter. Figure 9 shows the time of the actual alarms
issued by JMA’s EEW and compares them with alarms
which an on-site FREQL system would have been able toissue, based on a simulation using the recorded waveforms.
The depth of this earthquake was approximately 8km below
the surface. The alarm from JMA’s EEW was issued 3.5
seconds after the event detection to the primary customer
and one second later to the public, which is equivalent toabout 10 seconds after the earthquake occurrence. Although
the timing of the alarm in this case was faster than the
averaged processing time of 5.4 seconds (see Figure 7), theBlock diagram of On-site EEW in
Suzukakedai Campus of Tokyo Tech.

Rescue teams involved in the aftermath of the 2008
Iwate-Miyagi-Nairiku Earthquake also benefited greatly
from the portable FREQL.
FREQL were used also in some private railway
companies in Tokyo metropolitan area for EEW, and are
testing now in a nuclear power plant, semiconductor
facilities and so on. We expect in near future FREQL will be
actively involved in plants and worksites to mitigate
P-w ave Alarm ( RI=1.5) by FREQL
Triggered Alarm (5HzPGA=10Gal) by AcC o
Beginning of Principal Motion
Occurrence Tim e of Maxim
umMotion
MotionaximumTime in seconds from Earthquake Occurrence

45
40
35

FREQL Quicker Zone

30
25

im
Max

u

otio
M
m

n

Damaged Area

20
15
10
5
0
0

A
L
Q
FRE

10

20

30

40

Alarm by JMA
JMA
Alarm

larm
50

60

70

80

90

100

110

120

Epi-central Distance in km

Figure 9 Comparison of EEW timing between JMA and FREQL/AcCo for the 2008 Iwate-Miyagi-Nairiku Earthquake

Time in seconds after Earthquake
Occurrence50

The 2009 L'Aquila Earthquake
2009/4/6, Mw6.3, h9.5km

45
40

RI>2

Maximum RI = 5.68 (MMI = 9.43)
at AQV (epicentral distance 4.4km)

35
30

S-waveRI>3

RI>1

2 (3.6)4 (6.8)25

3 (5.2)1 (2.1)4 (6.8)

20

RI>4

15
10

RI_maxRI>40 (0.5)

P-wave3 (5.2)5 (8.4)

RI>0

Figures in brackets correspond to MMI

RI>54 (6.8)0

10Onsite FREQL Alarm: RI>1.5
First FREQL Alarm: RI>1.5

5
0
20

30
40
50
60
70
Epicentral Distance in km

80

90

100

Figure 10. Timings of P wave arrival, FREQL warning, S-wave arrival and Maximum motion arrival:
RI means Realtime Seismic Intensity; figures in brackets are corresponding to MMI.
warning was still only delivered after the beginning of thestrong motion. In contrast to this, FREQL is expected toissue an alarm 0.2 seconds after the P-wave detection in thedamaged area, i.e. the time margin before the beginning of
the strong motion is several seconds, even at the epicenter
itself.
In general, one can safely state that the on-site alarm
issued by the FREQL is faster than that issued by JMA’s
EEW within an area of about 50 km from the epicenter. For
epicentral distances over 50 km, the on-site EEW of the
FREQL is issued more than 10 seconds before the onset ofstrong motion. The average processing time of JMA’s EEW
is 5.4 seconds, but to transmit the information from thedetecting site to the processing center and the warning to theuser will take some additional seconds. Typically, thetransmitting time from the detecting site to the processing
center, and from there to the users is estimated to be a totalof around two seconds, increasing the time difference
between receiving the warning from JMA and from FREQL
more.
The
experience
of
the
2008
even
Iwate-Miyagi-Nairiku Earthquake confirms this finding forlocations with over 100km of epicentral distance. Until today,
there has been no example where JMA’s EEW was able toeffectively be used for disaster prevention by means of early
warning
8.2. A Near Event-1
The 2009 L’Aquila Earthquake, M6.3 and 9.5 km depth,
was occurred in central Italy at 6th April 2009. This
earthquake caused severe damage in the epicentral area.
Figure 10 shows a result of simulation for the 2009
L’Aquila earthquake using strong motion records.
According to this figure, FREQL was expected to get a few
seconds as a leading time at even epicentral area. It is very
short time, but during the leading time people could be
evacuate into some sturdy desk before falling down the flooror the ceiling. It is needless to say that the most importantmeasure is to build the structures enough earthquake-proof.
Even after the reinforcement against the earthquake, because
there is still risk on the falling objects, the repeatedemergency drills are essential to acquire the image of thedamage situation after the earthquake for the reasonablecountermeasures. Anyway there is no system to issue theearthquake alarm quicker than on-site FREQL, so it isadvisable to take proper countermeasures without
exaggerating the effect of EEW.
8.3. A Near Event-2
The 2010 Jiansian Earthquake, M6.4 and 23 km depth,
was occurred in mountain area of southern Taiwan at 4th
March 2010, 8:18:52.14 of local time, according to the CWB,
Central Weather Bureau. Figure 11 shows distribution mapof seismic intensity RI and 5HzPGA. The strong motion wasobserved at the plane area apart from epicenter and damage
was occurred in this area. This interested phenomenon wasstrongly reflected by the amplification of the sedimentary

Figure 11 Distribution of Realtime Seismic Intensityand 5HzPGA of the 2010 Jiansian
Earthquake, Taiwan

Time in seconds from2010/3/4,00:18:52.1440

台湾・甲仙地震 M6.4, h22.64km

35

5.1

Maximum Motion
4.8

5.0

30

5.5 4.5

20
4.8 5.0
4.3 3.8
5.3

15

5
4
40Gal ↱
10Gal ↗
5HzPGA

10
5

4
RI = 2

5.4

25
5.1
5.9 5.6

3.9

1.5

5.0

1
40Gal Alarmat ISCER10

10Gal

P-wave arrival
FREQL Alarmat ISCER10

3

Fastest FREQL Alarm

0
0

50

100

Epicentral Distance in km
Figure 12 Simulation Result of FREQL Alarm for the Jiansian Earthquake
surface ground on the plane. In the area a running Taiwan
Shinkansen train with 300km/h was derailed, but no injured
passenger and no damage to the structures.
Figure 12 shows a simulation result of FREQL alarmusing strong records of the CWB with changing of the RI.
The 40 Gal alarm, which is a triggered alarm over 40 Gal of
5HzPGA, was issued at 8:19:10 to the derailed train.
FREQL alarm should be issued at 8:19:02, 8 seconds earlier
than the 40 Gal alarm. FREQL alarm issued 0.8 seconds
after P wave detection proceeding to the strong motion withover 7 seconds. It is clear that the FREQL alarm proceeding
to the strong motion with over three seconds at even the
focal area.
8.4. A Huge Distant Event
A huge earthquake, Mw 8.8 and 47 km depth, withtsunami was occurred along the coastline of Chili in 27th
February 2010, 3:34 of local time. Figure 13 shows asimulated result using the waveform data set of Chili
University. According to this the strong motion over 5 of RI,
correspond to 8 of MMI, were maintained several tens
seconds even at several 100 km apart from epicenter. This is
the property of a huge earthquake of almost Mw 9. The
on-site alarm by FREQL in focal area will be issued justafter P wave detection. In the area far from the epicenter, theon-site alarm by FREQL will be delayed from P wave
detection. But the leading time proceeding to the strong
motion over 4 of RI, correspond to 7 of MMI, were
estimated as follows; over 7 seconds for the focal area andseveral tens seconds for distant area. Of course the leading
time of a network alarm by FREQL will be longer, but theon-site alarm by FREQL will be present enough leading
time needless communication facilities which often broken
at big disaster occurrence.

9. WHAT INFORMATION IS REQUIRED FOR
EARTHQUAKE DISASTER MITIGATION?
From the operational side, there are three pieces of
information relevant to realtime earthquake assessment:(1) an early warning before the onset of the strong shaking
for the area of certain damage,(2) information before the shaking starts about the area thatwill not be damaged, and(3) a precise and detailed estimate of the location and extent
of the area where serious damage can be expected.
The most important issue for public agencies is to havea reliable assessment as listed in Item (3) above, so that
rescue activities in the damaged areas can be initiatedimmediately. For the public agencies it is impossible todeliver information as under Item (1) due to the longprocessing and communication times. Only on-site early
warnings can deliver that information. In general, the early
warning can only be used to trigger individual or locally
based social group help or action. Governmental assistancewill mainly focus on the rescue work in the seriously
damaged areas evaluated by information as under Item (3).
Information as under Item (2) has no relevance to damage,and is unnecessary information for disaster prevention. For
most events, unfortunately, JMA’s EEW seems usually only
capable to deliver information as under Item (2).
The warning must be delivered rapidly and beaccompanied by information for a rational response to theevent. The information as under Item (3) above is essential
to decide on such actions. It is important to receive rapid and180

The 2010 Chile Earthqwuake
2010/2/27, Mw8.8, h47km

170

-32
ROC1

Time in seconds from 2010/2/27, 06:34:00

160

-33

Rimax
5.13

150
140

4

120

Realtime Intensity 4

590

Realtime Intensity 5

-37

RI 3

CCSP

-38

-39

4

-40
-74

-73

-72

-71

-70

3

Rimax
5.76

60

-36

RI 1.5 Alarm

80
70

rapid rise
in RI

Rimax
5.30

5

110
100

-35

Rimax
5.11

130

CLCH
ANTU

-34

2

50
40
30

P wave Arrival

20
10

The time of Earthquake Occurrence

0
0

100

200

300

400

500

Epicentral Distance in km

Figure 13 Simulation Result for the 2010 Chile Earthquake of Mw 8.8
accurate earthquake information from organizations such as
JMA in Japan, but it is also important not to restrict thedelivery of the information as under Item (3) from otherorganizations, such as local universities or Institutions.
As mentioned above, the best possible earthquake
assessment (made in realtime) is essential information to
specify the extent and location of the seriously damaged area,
to enable the implementation of immediate and appropriate
emergency response directly after the event. Whileearthquake observation systems designed for scientificresearch must be able to determine the exact location of theevents, UrEDAS has deliberately been designed to estimate
the earthquake parameter only in an approximate way to beable to issue the warning and the required response action in
the shortest possible time.
Public organizations should deliver information on theearthquake parameters not only for the main shock but also
for aftershocks as soon as possible. However, from theviewpoint of earthquake disaster prevention, it is more
important to deliver accurate earthquake information as
quickly as possible rather than to deliver a “late” early
warning. For the most appropriate and quick response after
the earthquake, the “actual observed” seismic motion as
intensity, not an estimated value, is the most important
information because the degree of damage can be estimatedfrom it.

10. PROBLEMSIN
THE
DELIVERYOF
EARTHQUAKEWARNINGSBY
THE
NATIONAL AUTHORITIES

If only one authority can issue warnings, allorganizations and the general public must rely on it. This
leads to the general public, as well as organizational
managers develop the habit of waiting for the informationfrom the authority instead of using some reasonableself-management for protection and mitigation. On the other
hand, if other organizations are also permitted to issue
warnings, all involved must be aware of that they do this on
their own risk and must take full responsibility for theirwarnings and possible consequences.
If issuing warnings is based on a law or regulation,organizations and individuals responsible for issuing
warnings develop a strong tendency to wait with the warning
until the last moment (which may be too late). On theorganizational level, promulgation of such warnings might
be slowed down for fear of reprisals or bad reputation.
In Japan, this trend is quite obvious in the ways inwhich tsunami warnings or cautions are given. By law, only
JMA is permitted to issue tsunami information in the form of
an official tsunami warning. However, as it is commonly
seen on TV news in Japan, the source of such tsunami
information is not clear and in most cases, the accuracy of
the information on which the warning is based is doubtful.
This situation can lead to a considerable lack of reliability
with many false warnings and cautions, commonly know as
the “crying wolf syndrome”.
It became very obvious that an M7 class earthquake
causes catastrophic damage especially in the area close to
the epicenter. Although M7 class earthquakes are quite
common in Japan, it is a potentially fatal flaw in the warning
system that the JMA’s EEW cannot issue a timely andaccurate estimate of the large motion in the catastrophicallydamaged area. If the early warning for the large motion isdelayed too long (for whatever reason) it becomes
meaningless.
For M8 class events (which occur statistically once
every several tens of years in Japan), the JMA’s EEW seems
to be capable to issue a warning with a useful time margin
for the strong motion. Yet such a warning is only useful, if it
is readily available for the damaged area more than 50 km
from the epicenter. This, however, might not be the case,because in such a serious situation it is quite possible that the
information is lost or delayed by problems in thecommunication system. In contrast, an on-site alarm systemis, by definition, not exposed to these problems and can issue
a warning or alarm before the onset of the large earthquake
motion.
On-site alarm equipment such as the FREQL, iscapable to issue the alarm in as short a time as 0.1 seconds
after the P-wave and can thus issue the warning before theonset of the large earthquake motion, even for locations
close to the epicenter. If then a local FM radio station would
broadcast the FREQL information, there would be a time
margin for preventative action within the damaged area.
Unfortunately, after December 2007, there is a hesitation for
implementing of such a system because it might violate alaw restricting the authority to issue warnings to JMA.

11. CONCLUDING REMARKS
Realtime earthquake warning was initially aimed at
disaster prevention for the train system in Japan, but is by
now used in many other environments as well. To be ofwide-ranging benefit, the time margin of the warning must
be very short on a time scale of seconds to enable quick
action by the general public, such as to seek shelter (likeunder a sturdy desk) or to evacuate immediately to a
pre-determined safety zone. The disaster prevention activity
must be based on the actual seismic motion in thesurrounding area, not an estimated one or one for some otherlocation.
It is an open question whether or not an appropriate
earthquake early warning system is in place in Japan today.
Clearly, there has not been much discussion about this issue
until today. It seems that the (so far futile) attempt to develop
a reliable earthquake prediction system is getting much more
attention than the fact that an effective and reliable
earthquake early warning system is a reality and readily
available.
It is clear that the primary preventative action by thepeople at the time of the earthquake is to keep away fromplaces where they could be hit by falling or loose objects. To
be able to do this obviously requires a timely and immediate
warning to be issued.
The earthquake information including warning is noteffective for disaster prevention to be provided exclusively
as a national project. A warning cannot prevent the possible
collapse of structures, but it can most definitely assist people
evacuating from collapsing facilities. A prompt and reliable

earthquake warning should become part of the daily life of
the people in Japan. National organizations should be able tospecify the area of expected catastrophic damage accurately
and initiate rescue operations without delay based on
information from responsible and capable organizations in
realtime.

Acknowledgment:
The author wishes to thank Tokyo Fire Department for theircooperation in the implementation the systems: FREQL-based early
warning system. The simulation described in this article used the
waveform data from K-NET and KiK-net of NIED, National
Institute of Earth Science for Disaster Prevention, Dr. Kai-Wen Kuo
of the Central Weather Bureau of Taiwan and Mr. Jerry Li of
Taiwan High Speed Rail Corporation. I wish to express my sincere
thanks to all individuals that contributed to this paper.
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