1. Challenge H: For an even safer and more secure railway
Practical Use of the Earthquake Early Warning (EEW) System for Shinkansen
Shinji Sato, Kimitoshi Ashiya, Shunroku Yamamoto, Naoyasu Iwata,
Masahiro Korenaga, and Shunta Noda
Railway Technical Research Institute, Hikari-cho, Kokubunji, Tokyo Japan
1. Introduction
Japan is a distinguished country of earthquake occurrence in the world. 100,000 earthquakes or
more are recorded every year according to the published data of the Japan Meteorological Agency
(JMA). This means that about 300 or more earthquakes occur per a day on the average somewhere
in Japan. According to the Cabinet Office, the Government of Japan, Japan accounts for about 20%
of all the M6 or more earthquakes occurring in the world. In view of this situation, Japan National
Railway (JNR) had established a lot of counter measures for a long time. In order to decrease the
earthquake damage of the railway soft measures such as stopping the train immediately after the
earthquake occurrence before a big shake reaches to the train are important in addition to hard
measures such as earthquake resistance improvement of the structure and installment of the
derailment measures etc. We have promoted development of the Earthquake Early Warning (EEW)
system which surely catches the P-wave, judges the range of the earthquake damage generation from
this information instantaneously, and stops the train operation. Here, the research and development
of the practical use of the EEW system for Shinkansen, details of the system and the study to be
continued for the future will be described.
1980 2000 20091960
Compact UrEDAS
(1996 2004)
UrEDAS
(1992 2004)
The 1st
generation
The 2nd generation
The 3rd generation EEW seismograph
(2004 )
Niigata Pref. (1964) M7.5
Ooi river (1965) M6.1
Tokachi Off (1968) M7.9
Miyagi Off (1978) M7.4
Southwest Off Hokkaido (1993) M7.8
South Hyogo Pref. (1995) M7.3
Mid Niigata Pref. (2004) M6.8
Niigata Pref. Chuetsu Off (2007) M6.8
Middle Japan Sea (1983) M7.7
Kushiro Off (1993) M7.5
Fig.1 Development of EEW system for Shinkansen

2. Challenge H: For an even safer and more secure railway
2. Development of EEW system for Shinkansen
Fig.1 shows the development of the practical use of the EEW system for Shinkansen. The first
generation of development is installment of a seismograph that outputs warning when the shake more
than the criterion is detected. In the second generation of development, the EEW system estimate
the amplitude of the shake of S-wave by detecting P-wave was put to practical use. When the Seikan
undersea railway tunnel was opened to the commercial use, UrEDAS (Urgent Earthquake Detection
and Alarm System) that was the EEW system for railway was put to practical use for the first time in
1987. At that time UrEDAS didn’t stop the train directly and only had the function to display the
information where the earthquake had occurred on the train control panel. UrEDAS had been
improved since then, and its practical operation was started for the first time in the world as a system
that had the warning judgment and train control function along with introduction of Tokaido Shinkansen
"Nozomi (300 series)" in 1992. In addition, when Hokuriku Shinkansen (between Tokyo to Nagano)
started a business in 1998, Compact UrEDAS of which P-wave detection technique improved, was
introduced. In the third generation development, a new seismograph was developed that was
equipped with P-wave detection algorithm was put into practical use
(4)
.
The reason why this system could be easily installed into Shinkansen system was become
Shinkansen system is such that it can be easily integrated with this system. The railway is a system
in which the ground equipments, the vehicles, the signals, communication systems, operation, and
management etc. are highly integrated. The Shinkansen vehicle has the function that an emergency
brake operates automatically when power supply is stopped. Integrating such Shinkansen vehicle’s
function with the Shinkansen substation function to stop power supply automatically linked with the
operation of the seismograph, the EEW system has been developed to be used as a software
countermeasure against the earthquake damage for Shinkansen. There is no precedent for
introduction of similar systems in the transportation fields such as the road and air transport in Japan.
3. Feature of EEW system for Shinkansen
3.1. System Structure
In this system, it is a prerequisite that, in order to secure the maximum reliability as an earthquake
disaster prevention system used in the railway, the system should operate if only one seismograph is
functioning. This system is composed of two kinds of seismographs namely the seismographs
installed along the railway-tracks to detect an earthquake occurring along the railway-tracks or large
scale earthquakes and the Coast line seismograph installed in the places other than the area along
railway-tracks, a relay server and a supervisory terminal which consolidates received from the
seismographs and monitor system. There is EEW system of the JMA with a similar function. The
difference between our system and JMA exists in the warning judgment part. To cope with
occurrence of the troubles of the power supply and the communication, our system does the warning
judgment and the trains stop judgment with only one seismograph, while in the JMA system, the

3. Challenge H: For an even safer and more secure railway
warning judgement is done at the control server Fig.2 shows the comparison of the respective
system configurations. The function of each seismograph is now explained as follows.
Fig.2 Difference between EEW system for Shinkansen and the one for JMA
3.1.1 Railway-tracks seismograph
This is a seismograph set up in the substation to cope with the earthquake that occurs in the
places along the railway-tracks. Moreover, this seismograph cuts off a power supply to stop
Shinkansen trains by outputting 24V contact signal when the earthquake occurs. The purpose of
setting up the seismograph in the substation is to surely transmit 24V contact signal to the substation.
On the other hand, although it is advantageous to set up the seismograph in the substation from the
view point of transmission of information, the protection equipment and the seismograph must be so
prepared as to cope with the electromagnetic influence of the adjoining transformation installation that
deals with AC2,500V.
3.1.2 Coastline seismograph
The coastline seismograph is a seismograph set up along the coastlines to detect promptly the
large-scale earthquake that occurs in the vicinity of an ocean deep. It is sometimes set up outside the
right of way. In that case, there is no big difference between coastline seismograph and that of JMA
with respect to the installation environment.

4. Challenge H: For an even safer and more secure railway
Both the seismograph along the railway-tracks and the coastline seismograph have the detection
function of the P-wave and S-wave. Moreover, a mechanical seismograph that keeps operating for a
long time even if the power supply is cut off is juxtaposed to cope with breakdown of the seismograph
for EEW. Fig.3 shows each seismograph.
3.2. Earthquake detection and train stop judgment technique
Generally, P-wave reaches the railway track concerned earlier then S-wave. If the scale of
earthquake (magnitude) and the epicenter can be known before S-wave of the large amplitude
reaches the railway tracks, the braking instruction can be given to the train ahead of time, and
consequently the safety of the train operation during earthquake occurrence can be improved. Here,
the detection method of the P-wave and S-wave, and how to judge the train stop will be described.
3.2.1. P-wave detection and train stop judgment technique
Within 1 to 2 seconds after detecting P-wave, the EEW seismograph estimates the earthquake
parameters namely epicentral distance, epicentral azimuth, and magnitude as shown in Fig.4.
We call this estimation process B - Δ method. In addition, the range of damage area is estimated from
the estimated epicentral distance and magnitude using the empirical equation. We call this estimation
process M - Δ method. Using these two methods, EEW seismograph judges train stop (power supply
cut off), only in the case EEW seismograph (observation site of Fig.4) is located within the estimate
damage area. Earthquake parameter estimation (B - Δ method) and M - Δ method will be explained in
the following.
Fig.3 Seismograph system
(Left EEW seismograph Right mechanical seismograph)

5. Challenge H: For an even safer and more secure railway
Epicenter
Estimated Damage Area
Depends on Magnitude
Estimated Azimuth
Observation Site
Estim
ate
Epicenter
North
Fig.4 P-wave detection and warning judgment method
(a) B – Δ method
Generally, the P-wave propagates the site concerned the earliest among the seismic ground
motion elements, and wave velocity is 5 to 7 km/second in the bedrock. We will briefly explain here
the outline of the method of estimating earthquake parameters based on the P-wave (Refer to Odaka
(2)
for details). The EEW seismograph for the Shinkansen system always measures the acceleration
data in the three components (NS,EW,UD) with 100Hz sampling. The IIR filter processing for P-wave
detection is applied to the obtained acceleration data as shown in Fig.5. Next, the fitting processing
by the eq.(1) is applied to the envelope curve of the absolute value of amplitude of UD component of
the data obtained within 1 to 2 seconds after earthquake is detected.
Fig. 5 IIR-Filter design for P-wave detection.
Frequency(Hz)

6. Challenge H: For an even safer and more secure railway
y(t) = Bt exp(-At) (1)
Coefficient B included in the above eq.(1) indicates the tendency of the amplitude increment of the
first movement part of P-wave, and it is confirmed that it has a good correlation with the epicentral
distance as shown in Fig.6. The epicentral distance is obtained from the tendency of the amplitude
increment of the first movement part of P-wave (Coefficient B) by using this relationship.
Fig. 6 Relationship between the coefficient B and the epicentral distance Δ
If the epicentral distance is estimated, the magnitude is calculated by the empirical equation
prepared beforehand that shows the relation between the peak magnitude and the epicentral distance.
When a large earthquake occurs, the magnitude that increases gradually is calculated accurately by
keeping analyzing the maximum amplitudes every sampling. Fig.7 shows the estimation process of
these earthquake parameters.
Earthquake
Detection
Time
Amplitude
Data Length
(1 - 2 second)
P-wave
Amplitude Increase Ratio
Epicentral Distance
Epicentral Distance
Magnitude
Maximum Amplitude
S-wave
Fig. 7 Estimation process of earthquake parameters by a new seismograph

7. Challenge H: For an even safer and more secure railway
(b) M - Δ method
Next, we will explain the processing how to control the train operation based on the estimated
epicenter distance and magnitude. The train stopping is decided in case the extent of the shake of
structure reaches the level at which the structure will be damaged. For this decision, it is necessary
to accumulate the various records of the past earthquake damages. M – Δ diagram is prepared
based on these records of the past earthquake damages (Refer to Fig.8). In Fig.8, the past damage
records are plotted, and the area where the plotted data are enveloped should be the train control area
(Fig.8 shaded part). For instance, the decision to stop Shinkansen train is executed at once, in case
an earthquake occurs and its estimated magnitude is 7 and its estimated epicenter distance is 20km,
because the data consisting of M and Δ is contained within this area. This technique was adapted
along with the practical use of UrEDAS in 1992, and has been reviewed every time a damaging
earthquake occurs. It can be said that this M – Δ figure offers a simple and reliable train stop decision
technique because decision is executed based on two parameters of the estimated epicenter distance
and the estimated magnitude.
3.2.2. S-wave index
The vector amplitude of horizontal 2 components acceleration that passed the JR warning filter
(JR filter) is used as an index to controls train driving for both Shinkansen and domestic railways. The
JR filter is based on the design standard of the filter established on as JNR standard in 1984. Fig.9
shows frequency characteristic of the JR filter. It is understood that pass-band of this filter is
corresponding to predominant frequency of P-wave and S-wave. When the horizontal, vector
amplitude exceeds 40gal S-wave is issued.
Fig.8 Relationship between Magnitude and Epicenter( Δ )

8. Challenge H: For an even safer and more secure railway
3.3. Communication between seismographs
After Shinkansen derailment by the Mid Niigata Prefecture Earthquake (2004), the earlier alarm
output has been demanded by JR companies. The function of information exchange on P-wave
warning among the seismographs along the railway-tracks has been newly added to the system of the
third generation. This function is called a seismograph two-way communication function, and is
shown in Fig.10. Thanks to this function, a prompter warning judgment has become possible
because the warning judgment can be made even in the region where neither P-wave nor S-wave has
arrived.
Fig.10 Seismograph two-way communication
4. Simulation for the Mid Niigata Prefecture Earthquake in 2004
The operation simulation of the seismograph in the Mid Niigata Prefecture Earthquake (2004) has
been executed based on the judgment technique of warning of the P-wave and S-wave that has been
shown up to now, and lead-time after giving warning has been examined. The earthquake data used
Fig.9 IIR-Filter Design for S-wave alarm

9. Challenge H: For an even safer and more secure railway
is those of K-NET of National Research Institute for Earth Science and Disaster Prevention (NIED)
recorded within 20km from the epicenter. It is thought that the operation of the actual JR
seismographs have recorded also almost the same data. The arrangement of the seismographs is
shown in Fig.11 and the simulation results are shown in Table 1.
Koide
Ojiya
Tookamachi
Nagaoka
Nagaoka-Shisho
EpicenterJyo-Etsu
Shinkansen
Jyo-Etsuline
Tadamiline
Shin-Etsu
line
Iiyamaline
Fig.11 Arrangement of the seismographs
( site of seismograph of NIED)
Table 1 The simulation results
P-wave arrival
time
S-wave arrival
time
P-wave warning
time
S-wave warning
time
Ojiya 7.05 17:56:02.93 17:56:03.50 - 17:56:03.74 -
Koide 10.60 17:56:03.42 17:56:04.27 17:56:04.35 17:56:06.92 2.57
Nagaoka-shisho 15.11 17:56:03.90 17:56:06.30 17:56:04.15 17:56:08.02 3.67
Nagaoka 16.87 17:56:04.07 17:56:06.65 17:56:04.84 17:56:07.29 2.94
Tookamachi 21.02 17:56:05.40 17:56:11.90 17:56:10.33 17:56:12.88 8.53
Site Name
Epicentral
Distance
Manual Detection time Simulation result
Lead-time
(sec)
According to JMA the earthquake occurred at 17:56. P-wave warnings were issued from all
station except Ojiya. In Ojiya P-wave warning was not issued, because vertical motion was extremely
larger than criteria, S-wave warning was issued immediately after P-wave arrival. From the result
shown in Table 1, Lead-time is estimated to be almost 3 seconds in the neighborhood of the epicenter.
It is thought that the benefit of the lead-time is limited for the trains running in the vicinity of the
epicenter because Shinkansen trains need a few minutes to be stopped. However, it is considered
that the benefit of the lead-time is high for the trains that run in the area from the epicenter.

10. Challenge H: For an even safer and more secure railway
5. Improvement of seismograph
To stop Shinkansen as fast as possible after the earthquake is detected, the seismograph is
basically arranged in the substation placed along railway-tracks. However, it is necessary to consider
the occurrence of the malfunction by the electromagnetic radiation which is usually strong in the
substation. Therefore, reliability improvement of the hardware of the seismograph for the
electromagnetic radiation is expected. In order to apply the EMC standard to the seismograph
quantitative evaluation the tolerance to the electromagnetic radiation carried out now. EMC standard
is a standard by which it is proven to make the influence given to no disorder of operation even if the
electromagnetic radiation influences an electronic equipment such as seismographs or nor other
electronic equipment a minimum. First of all, the electromagnetic radiation of strength of the
electromagnetic radiation around the seismograph was measured in the substation where the
seismograph was set up. Seismograph EMC examination based on IEC61000 was executed in
special equipment based on this test result as shown in Fig.12. We considered the test result, and a
new seismograph is being produced now. We will want to judge right or wrong of the adoption as
seismograph EMC specification while seeing the effect of a new seismograph.
Fig.12 The EMC test for Seismograph
6. Summary
Here, we presented the details of the EEW system in Japan and a concrete content of the EEW
system now in use. The seismograph used in the Shinkansen system has the P-wave and S-wave
warning function. Moreover, power supply can be stopped when judged as dangerous by each
seismograph. In addition, earthquake information can be exchanged among the seismographs, and
even the seismograph to which P-wave has not reached yet has the function to do the warning
judgment. This system is actually operated for Shinkansen now. We think that based on the

11. Challenge H: For an even safer and more secure railway
experiences up to now, it is necessary to continue the research and development of the algorithm
concerning a prompter warning judgment (software) and the composition equipment (hardware) that
does the steadier operation. Further, in view of the coming Shinkansen speed up to more than
300km/h, various approaches should be examined in future, aiming at achieving more reliable EEW
system, while corresponding flexibly to the change of the railway system.
Reference
(1) Cabinet Office, Government of Japan, Outline of earthquake measures of our country,
http://www.bousai.go.jp/jishin/chubou/taisaku_gaiyou/pdf/hassei-jishin.pdf (in Japanese)
(2) Odaka T., Ashiya K., Tsukada S., Sato S., Ohtake K. and Nozaka D.: A new method of quickly
estimating epicentral distance and magnitude from a single seismic record, Bull. Seism. Soc. Am.,
Vol.93, No.1, pp.526-532 (2003)
(3) Tsukada S., Odaka T., Ashiya K., Ohtake K., Nozaka D.: A new algorithm for EEW system using
P-wave envelop, Zishin2, Vol.56, No.4, pp.351-361 (2004) (in Japanese)
(4) Sato S., Taya S., Ashiya K.: Development of seismograph for warning that uses new earthquake
parameter presumption algorithm, RTRI Report, Vol.16 No.8, (in Japanese)
(5) Iwahashi H., Iwata N., Sato S., Ashiya K., Practical use of earthquake early warning system, RTRI
Report, Vol.18 No.9, (in Japanese)