13th World Conference on Earthquake Engineering
Vancouver, B.C., Canada
August 1-6, 2004
Paper No. 908

UrEDAS, URGENT EARTHQUAKE DETECTION AND ALARM
SYSTEM, NOW AND FUTURE
Yutaka NAKAMURA 1SUMMARYUrEDAS, Urgent Earthquake Detection and Alarm System, can realize the real-time early earthquake
detection and alarm system in the world. There is a local government that has realized a tsunami warning
system using real-time estimated earthquake parameters as magnitude and location, distributed byUrEDAS.
On 26th May 2003, the Miyagiken-Oki Earthquake was occurred. It was so large that the maximum
acceleration of about 600 Gal was observed along the Shinkansen line and 23 columns of the rigid frame
viaducts (RC) were severely cracked. This earthquake occurred on the business hours of the Shinkansen.
As expected, coastline “Compact UrEDAS” along the Shinkansen took out the early P-wave alarm before
the destructive earthquake motion and the validity of this system was proved for the first time.

INTRODUCTIONUrEDAS is the only real time P-wave alarm system over the world on practical use. It is characterized tobe able to process digitized waveform step by step without saving. Amount of procedure does not differs
either earthquake occurs or not, so failure because of over load will not occur.
The 2003 Miyagiken-Oki earthquake (Mj 7.1) occurred on 26th May, Compact UrEDAS worked asexpected. It was for the first time that the validity of the early warning system was verified undercircumstances of big earthquake such as rigid frame viaducts of Shinkansen were damaged.
In this paper, the present condition of P-wave early detection system UrEDAS will be viewed referring tocases at work, also result of test observation where faults exists will be reported. Then new real time dataprocessing system for next generation will be considered.

PRESENT OF UrEDAS AND ITS FUNCTION
There are two types of UrEDAS at present; “UrEDAS” and “Compact UrEDAS”.
Function of the UrEDAS is estimating magnitude and location of earthquake by P-wave and issuing thealarm to places which may cause damage. Compact UrEDAS will evaluate whether the earthquake will be
1Dr., System and Data Research Co., Ltd., Tokyo, Japan. Email: yutaka@sdr.co.jp

Tokaido Shinkansen, UrEDAS, since 1992
Sanyo Shinkansen, UrEDAS, since 1996
Tohoku, Joetsu and Nagano Shinkansens,
Compact UrEDAS, since 1998
Teito Rapid Transit Authority (Subway),
Compact UrEDAS, since 2001
Kushimoto Tsunami Alert System,UrEDAS, under testing
Niigata

Hachinohe
MoriokaMiyagiken-Oki Eq.
Sendai

NaganoHakataHiroshima
Geiyo Eq.

Kyoto

Osaka

NagoyaTokyo

KushimotoFigure1 The distribution of UrEDAS and Compact UrEDAS in Japandestructive or not, and will alarm if need. UrEDAS and Compact UrEDAS can issue the alarm in case ofearthquakes within range of 200 km and 20 km, respectively.
After the development of prototype UrEDAS in 1985, test observation had been continued. Practicaloperation was started partly at Omaezaki observatory for Tokaido Shinkansen by limiting its function in1990. When the Nozomi, new super express, was in operation, fourteen UrEDAS stations were at work
officially, with various improvement. At present the new type of UrEDAS took place in 1998 after theformer type. Figure 1 shows the distribution of UrEDAS or compact UrEDAS in Japan.
By the influence of the 1995 Hyogoken-Nanbu Earthquake, Sanyo Shinkansen has promoted the project ofinstalling UrEDAS, and started test operation immediately by using the data of three UrEDAS at west sideof Tokaido Shinkansen. Full operation started in November 1996 adjusting five new UrEDAS stations.
Along Tohoku and Joetsu Shinkansens and coastline alarm seismometer (45 stations) replaced to Compact
UrEDAS by the Spring 1997. Along Nagano Shinkansen which was under construction at that time,
Compact UrEDAS was newly installed (six stations), also installed coastline of the sea of Japan to prepare
for submarine earthquakes (five stations). Compact UrEDAS has not only P-wave alarm function but also
S-wave alarm function which does not need adjustment.
P-wave alarm was on operation since October 1998 after adjusting with suitable earthquake records. Since
then Compact UrEDAS has two level alarm function; P-wave alarm and S-wave alarm, which realized
quick and accurate warning.
Six Compact UrEDAS stations have been installed for Tokyo Metropolitan subway in March 1998 andstarted operation first only with S-wave alarm function, and from April 2001 with the P-wave alarmfunction.
Wakayama prefecture installed one UrEDAS station at Kushimoto, to build tsunami alarm system using
function to estimate hypocenter and its magnitude.
SDR has continued developing for the next generation system. Also UrEDAS has installed at Berkeley(BKS) and Pasadena (PAS), California, with cooperation with University of California and California

Institute of Technology, respectively. This research aims to search for the possibility of UrEDAS alarm
against tsunami earthquake at the Pan Pacific region and for the improvement of accuracy of detection atfault area.
And also UrEDAS has installed at Mexico City with cooperating with CIRES, Centro de Instrumentaciony Registro Sismico. CIRES is an organization to observe big earthquake around Acapulco and alarm toMexico City.

OPERATING SITUATION OF UrEDAS FOR RESEARCHBKS UrEDAS and PAS UrEDAS
PAS and BKS UrEDAS started observation in July 2000, and in February 2001, respectively. After
earthquake detection, these UrEDAS will send e-mail to whom concern in real time. Former type of PAS
UrEDAS was at work from September 1993 to August 1999, and observed the 1994 Northridge

PAS UrEDAS
BKS UrEDAS Figure 2 Circumstance of PAS UrEDAS and BKS UrEDASEarthquake.
BKS locates just above the Hayward fault while PAS is surrounded by faults (see Figure 2). Either stationis under bad condition. In spite of the influence of faults, PAS shows better estimate accuracy of focal
parameters than BKS, and performance of earthquake detection is effectively at both station.
After this, result of PAS is discussed with all the information delivered by e-mail.
Figure 3a shows the result of comparison between the UrEDAS estimation with recent system parameterand the result of USGS. This shows the error of magnitude is within 1.0, excluding distant earthquake(mainly above M6). Also preliminary hypo-central distance is presumed 0.5 to 2 times excluding distantearthquake over 1000km.

360270270

U S G S A zim uth

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180909000090180270
P A S U rED A S A zim uth0360998877U S G S M agnitudeU S GS M agn it u de

180

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96543221112345678090

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1100000U S G S EpicentralD istance in kmU S G S H y po c e n t r al D is t an c e

90180270
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1000100101110100100010000100000

P A S U r ED A S H y po c e n t r al D is t an c e

Figure 3a Estimated parameters by PAS UrEDAS
in realtime on site
UrEDAS

10000
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PA S UrEDA S EpicentralDistance Sim in km

Figure 3b New simulation results using
waveform recorded by PAS

Though epicentral azimuth shows error in particular direction which seems to have highly influence offaults, though it shows good result for distant earthquake. This indicates that influence of dislocation
remains near ground surface and can be expected the coming direction of distant earthquake motion.

9360

87U N A M M agnitude

U N A M A zim uth

270

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MEX UrEDAS
HypocentralDistance(secondary)

Figure 4 Estimated parameters by MEX UrEDAS in realtime on site

Some of waveform detected PAS UrEDAS and BKS UrEDAS is able to get from internet as cooperativework. Figure 3b shows example of simulation for improvement in accuracy using all the waveformrecorded in the period between October 2002 and October 2003. Basic technique is almost the same as
before [*] for estimating M by initial period and calculating the distance from initial amplitude. But thistime P-wave processing time is shorten to one second by three seconds as original. As a result, theaccuracy of estimated epicentral azimuth, hypocentral distance and magnitude are improved for thevariation of magnitude and distance. Especially the improvement of magnitude estimation using initialmotion during one second is interesting that it indicates a big earthquake know by itself to become bigfrom the beginning. Analysis may be improved by the stored data.
MEX UrEDAS
Mexico City (MEX) UrEDAS is installed in a junior high school where strong motion observation site #78
is placed by CIRES. Detected data of MEX UrEDAS will be sent by radio modem to UrEDAS center atCIRES head office and then the information will sent as e-mail to whom concern. This observation started
operation in December 2001. Before this test observation and internet connection were operated indifferent place from February 2000 to November 2001.

-3Velocity in 10 cm/s

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Figure 5 The waveforms of The Colima Earthquake recorded by UrEDAS

Figure 4 shows a result of observation which amplitude is over 0.001 cm/s. This shows that during Pwave, hypocentral distance is estimated distantly, and magnitude is underestimated about 1.0. Epicentral
azimuth and hypocentral distance during S-wave are substantially proper.

RECENT EARTHQUAKES DETECTED BY UrEDAS
The Colima Earthquake, Mexico (2003)
The Colima Earthquake occurred at 20:06:36 (Mexican standard time, MST) in January 21st 2003 near
Colima about 400km west from Mexico City where UrEDAS was installed. This earthquake caused severdamage near epicentral area. Information from MEX UrEDAS was received at Kunitachi, Tokyo at about
11:19:00 of the 22nd. (Japan Standard Time, JST) as followings,+Detected time of the earthquake: 22nd 02:07:51 (Coordinated Universal Time, UTC)
+Preliminary estimated focal parameters received at CIRES at 02:07:56, (UTC): Magnitude M6.8,
epicentral azimuth 280 degree clock-wise from north, hypocentral distance 232km, depth 134km.
Estimated epicenter is located in near the middle point between Mexico City and Colima at this time.
+Secondary estimated focal parameters received at CIRES at 02:08:53 (UTC): hypocentral distance
442km, depth 255km. Magnitude and azimuth are same to preliminary result. Estimated epicenter in final
is about 60km northeast from Colima
UrEDAS says, just after the primary wave of earthquake arrived, M6.8 earthquake is occurred in hundreds
kilometer west (according to experience, magnitude will be M7.8) Few minute later, when large motion
arrived, UrEDAS says epicenter turned out to be near Colima.
Figure 5 shows the waveform recorded by UrEDAS. This figure shows UD, NS and EW components inunit of 0.001cm/s, and indicator at 51 second and 105 second shows detected time of P-wave and S-wave
by UrEDAS, respectively.
From this waveform, the first motion was comparatively small, and after 4 seconds the first big P-wave
motion arrived. Because hypocentral distance was about 400km, duration of preliminary tremors wasabout one minute from first information sending to large motion.
UrEDAS has sent the first estimated result to CIRES center three seconds after P-wave detection, and justafter the S-wave detection it send secondary information immediately. CIRES system received theseinformation three seconds delay. It was 12 minutes delay in Japan to receive UrEDAS information after
the occurrence of the Colima earthquake. It seems to have a large time gap for internet communication,
though considering that the arrival of wave motion of earthquake in Japan takes 20 minutes, it is able tosay that information was received before the earthquake motion arrives. Considering of UrEDAS
observation result in Japan, it is expected to be accurate information of earthquake parameter and realize
accurate tsunami warning system.
The 2003 Miyagiken-Oki Earthquake
The Miyagiken-Oki Earthquake was occurred at 18:24:33 (JST) on May 26th with about 70km depth.
Compact UrEDAS at Rikuzentakada near the epicenter has detected this earthquake and immediately
issue early P-wave alarm. By the data recorded at Rikuzentakada station of KiK-net, since P-wave wasdetected at 18:24:44, so it is estimated that P-wave alarm had been issued at 18:24:47. By this alarm, train
operation was stopped between Sendai and Morioka before P-wave arrival. Rigid frame viaducts havecracked in northern part of this section.
This was the second damaging earthquake occurred near the Shinkansen line during business hours (thefirst earthquake was the 2001 Geiyo Earthquake) and the first earthquake for UrEDAS to alarm.
At the time of this earthquake there were eight trains between Sendai and Hachinohe, about 100km northfrom Morioka, where it had strong earthquake motion over 100 Gal (5HzPGA, see paper #). Fortunately
running train in high speed was only two trains, Yamabiko #59 and Hayate #26, others were very lowspeed or stopping at station. Figure 6 shows the relationship between the origin time, alarm issued time,
damaged area and also the position of trains from time table. If the earthquake occurred 10 minutes
thereabout before or after, it had high possibility for train to pass the track on the damaged structure.
Yamabiko #59 just left Kitakami station to north and has stopped immediately by early P-wave alarm. It
stopped 3km from the station, and 10km before the damaged structures.
Hayate #26 has passed Iwate-Numakunai station and was heading south by full speed. Earthquake motionof this area was estimated over 300 Gal. Because of running over hard ground or in tunnel, referring to theGeiyo Earthquake, passengers and crew might have not felt the earthquake. Alarm to Hayate #26 wasdelayed about 10 seconds comparing with the area south from Morioka alerted by early P-wave. So it isestimated that it was running at full speed without noticing the earthquake.

Figure 6 Situation of the Shinkansen when the 2003 Miyagiken-Oki Earthquake from the time tableIt shows that people on the running trains have difficulty to notice earthquake motion, thus earthquakealarm from outside is necessary.
And also, when the Geiyo Earthquake occurred many running trains encountered earthquake motion over
300Gal as Hayate #26 at the time of the Miyagiken-Oki Earthquake. Result of investigation of the Geiyo
Earthquake shows that trains running at full speed as like Nozomi or Hikari, in high-speed operation, atplaces such as in tunnel, passengers and crews won’t feel the motion. On the other hand Kodama,
stopping every station, running at low speed almost arriving to a station, passengers had felt fear that havethought the train will derail. Passengers of this train noticed that it was earthquake by looking outside andsaw destruction of roof or shake of electric wire.
When the Geiyo Earthquake occurred seismometer along the railroad near the focal area had alarmed
immediately and UrEDAS far from focal area didn’t alarm.
Yamabiko #59 just left Kitakami station and other trains at station might have felt larger motion than theGeiyo Earthquake though details are unknown. How the passengers felt in area where large motion
attacked is worthwhile to analyze.

REALTIME EARTHQUAKE DISASTER PREVENTION IN FUTURE
Information system causes insufficiency in occurrence of big disaster. As bigger the information systemgets weaker it is to disasters.
It is important to be equal to the occasion, thus rational and positive consciousness of disaster prevention
is required. Equipment for disaster prevention, firm and reliable system which work certainly is alsorequired. Therefore building systematic and individual system that works with high accurate priority ismore significant than building enormous system for disaster prevention. Turnover of mind “disasterprevention system” to “systematic disaster prevention” is required.
Firm, inexpensive and reliable system for disaster prevention should be built such as early warning andindicating evacuation even if rack of some accuracy. It is expected distributing many of these equipment
will be urged, cooperating with existent information system to reduce damage by disaster.

CONCLUDING REMARKSThis paper has viewed the present condition of UrEDAS the only realized system for early warning. To
apply the UrEDAS not only for railway system but also for other field not only toughness and reliability
but also easy to get it would be required than as now.
Also alarm seismometer or instrumental intensity meter is expensive for everyone. But the concept ofacceleration and seismic intensity should be known widely. Rational and immediate action for preventionof disaster will be possible, if exact vibration sense against earthquake motion could be produced on theireach sense. Then earthquake motion should be expressed as fixed quantity such as temperature, humidity
or time.

ACKNOLEDGMENTS
I would like to sincerely express my highest appreciation and gratitude to the following people for theirfriendly cooperation and great contribution to the setting up UrEDAS in each places, the checking thecondition of these system, and fruitful discuss for the observed results.

Prof. Hiroo Kanamori, California Technical InstituteProf. Fumiko Tajima, Hiroshima University
Dr. Robert A. Uhrhammer, University of California, Berkeley Seismological Laboratory
Mr. Juan Manuel Espinosa Aranda, Centro de Instrumentacion y Registro Sismico.
Mr. Samuel Maldonado Caballero, Centro de Instrumentacion y Registro Sismico
Mr. Jun Saita, System and Data Research. Co., Ltd.

REFERENCES
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Nakamura, Y, “Research and Development of Intelligent Earthquake Disaster Prevention System
UrEDAS and HERAS”, Journal of structural mechanics and earthquake engineering, Japan societyof civil engineers, No.531/I-34, pp.1-33, January 1996.
Nakamura, Y., “On the Urgent Earthquake Detection and Alarm System (UrEDAS)”, 9th worldconference on earthquake engineering, Vol. VII, pp. 673-678, August 2-9, 1988.
The Chugoku Shimbun, “Is Shinkansen Safe?” and “No clincher to countermeasure for derailment”,
reported at 1st and 2nd of May, News Special 2001, May 2001.
Proceeding of the study meeting for damage of recent earthquakes, the Miyagiken-Oki and theAlgeria Earthquakes (in Japanese), Japan society of civil engineers, 21st August 2003.
Nakamura Y., “On a Rational Strong Motion Index Compared with Other Various Indices.” 13thworld conference on earthquake engineering, paper #910, 2004.