Proceedings of the International Symposium on Engineering Lessons Learned fromthe 2011 Great East Japan Earthquake, March 1-4, 2012, Tokyo, Japan

Result of SUPREME (Super-dense Real time monitoring
Earthquake system for city gas supply) in The
Great East Japan Earthquake
Wataru INOMATA1 and Yuki NORITO2
1Manager, Department of Supply control and Disaster management, Tokyo Gas Co.,Ltd,
Tokyo, Japan, inomataw@tokyo-gas.co.jp
2
Department of Supply control and Disaster management, Tokyo Gas Co.,Ltd,
Tokyo, Japan, norito@tokyo-gas.co.jp

ABSTRACT: The Great East Japan Earthquake did not damage any important facilities
used by Tokyo Gas for city gas production and supply operations, but some low pressure
pipelines with low earthquake resistance were damaged, forcing the company to suspend
supplies of gas to about 30,000 homes to preserve safety. This report briefly describes
initiatives taken by Tokyo Gas to provide prevention from earthquakes and its responseto the Great East Japan Earthquake, which is centered on the super-dense real time
monitoring earthquake system, SUPREME.
Key Words: The Great East Japan earthquake, earthquake countermeasure, SUPREME(the super-dense real time monitoring earthquake system)

1. INTRODUCTION
To ensure the continuity of Tokyo Gas operations in anticipation of large earthquakes, thecompany has taken advanced measures to ensure the continuity of its operations: enacting regulations,establishing the earthquake disaster prevention PDCA cycle by, for example, conducting annual
integrated disaster prevention training with the participation of all employees, and at the same time,
preparing earthquake disaster measures in three major categories: preventive measures, emergency
measures, and restoration measures.
This report gives overviews of earthquake disaster prevention initiatives taken by Tokyo Gas andof its response to the Great East Japan Earthquake, which is centered on the super-dense real time
monitoring earthquake system, SUPREME.

2. EARTHQUAKE DISASTER PREVENTION INITIATIVES TOKYO GASAs stated above, Tokyo Gas has taken earthquake disaster prevention measures in three major
categories: preventive measures, emergency measures, and restoration measures. This section
discusses the specific contents of preventive measures and emergency measures which have absolutely
minimized disaster damage.

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Fig.1 Outline of the City Gas Supply System and Earthquake Safety Measures
2.1 Preventive measuresTokyo Gas’s basic policy is to takes preventive measures (equipment measures) for its LNG
terminal and high pressure and medium pressure gas pipelines which support the core of city gas
supply in our production and supply equipment, and to minimize damage caused by earthquakes.
LNG terminals and high pressure gas pipelines are designed and constructed under earthquake
resistance design guidelines of the Japan Gas Association and in-house standards, with the target
earthquake resistance of these standards defined as preventing leaks and maintaining their functions
under level 2 earthquake motion(The Great Hanshin-Awaji Earthquake class). The earthquake resistanceof existing equipment is also confirmed by design guidelines revised in response to the Great
Hanshin-Awaji Earthquake, and earthquake resistance measures are taken as necessary.
Medium pressure gas pipelines are, like high pressure gas pipelines, designed and constructedusing welded steel pipes with superior strength and flexibility. By evaluating the earthquake resistanceof the materials of existing medium pressure gas pipelines, and making individual detailed evaluationsof non-earthquake resistant materials confirmed to be susceptible to leakage under level 2 earthquake
motion, Tokyo Gas inspects the earthquake resistance considering the ground and the pipeline shape ateach location where these materials are buried and implements earthquake resistance measures at
locations they are found to be necessary.
2.2 Emergency measures
As stated above, production and supply equipment of medium or high pressure is designed andconstructed to maintain its functions under level 2 earthquake motion, but it is predicted that some low
earthquake-resistant low pressure gas pipelines will be damaged by large scale earthquakes. And toprevent secondary damage, the supply of city gas must be promptly and reliably shut off in regions
where damage is severe, so the following emergency measures are prepared.
a) Microprocessor-based gas meters
Microprocessor-based gas meters have been installed in the homes of all 10 million of ourcustomers as equipment installed as close as possible to end users’ premises in order to prevent
secondary disasters. These microprocessor-based gas meters, which are also equipped with vibration

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sensors, automatically shut off the gas to ensure customers’ safety when shaking in excess of 200gal(seismic intensity of about 5) has been detected.
b) Shut off supply to regions where damage is severe by SUPREME
A network of about 46,000km of low pressure gas pipelines sprawls across the Tokyo Gas supply
area, and this pipeline network is divided into 140 blocks (districts). Because each block is physicallyisolated from adjoining blocks, it is possible to separately shut off the supply of gas only to districts
where earthquake damage is severe.
Approximately 4,000 district supply governors, from which low pressure gas is transmitted, are all
equipped with SI sensors so they continuously monitor the scale of earthquake vibrations. On thedistrict supply governor, shut off valve which operate linked to the SI sensors are installed, and whenan SI sensor has observed 40 to 60 kine, which corresponds to seismic intensity of weak 6, its district
supply governor automatically shut off, stopping the supply of city gas.
In blocks where damage is severe and in blocks where the Tokyo Gas supply shutoff criterion(where the SI value obtained by the judgment use seismograph is 60 kine or more) has been reached,supply must be stopped promptly, but if there is a district supply governor where the threshold value
for automatic shut off within a block has not been reached, the supply of city gas continues. So inblocks where damage is severe, SUPREME permits shut off by a remote operation of all district
supply governor in order to quickly shut off supply to such blocks.
c) Estimating damage to low pressure gas pipelines by SUPREMESUPREME is equipped with a damage estimation equation prepared by performing factor analysis
of past damage to low pressure gas pipelines caused by the Great Hanshin-Awaji Earthquake, ofearthquake motion distribution/liquidation distribution, and of engineering geomorphologic
classification and type of pipeline (Fig.2). The damage estimation equation is an approximation
formula which statistically processes past damage, and it expresses the qualitative relationship-thelarger the shaking, the more severe the damage-so it is appropriate to estimate the approximate numberof damaged locations within an area with a large scale pipeline network.
SUPREME interpolates SI values for 50m meshes to calculate the number of damaged locations ineach mesh in real time, based on SI values for 4,000 locations observed after disasters and data ofgeotechnical investigations (local site effects on ground motion) obtained in advance. SUPREME isalso equipped with logic to calculate the PL value by the same process based on the observed SIvalues, to simultaneously estimate the risk of liquefaction (and to calculate damaged locations basedon PL values and damage rate).
Finally, it estimates the number of damaged locations in each block and uses the results to decide
to make a secondary emergency shut down decision and to enact restoration strategies.

Damage rate (damage locations/km)

4.0
3.5

SUPREME damage estimation curve

3.0

The Gereat Hanshin-Awaji Earthquake:threaded branch pipes are damaged

2.5
2.0
1.5
1.0
0.5
0.0
050

100
SI (kine)

150

Fig.2 Damage Estimation Curve of SUPREME

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200

3. RESPONSE TO THE GREAT EAST JAPAN EATHQUAKE
3.1 Initial Measures Centered on SUPREME
When this earthquake struck at 2:46 p.m. on March 11, seismic intensity of strong 6 was recordedin Hitachi City in the Tokyo Gas supply area, and seismic intensity from weak 5 to strong 5 wasobserved in a wide range in the supply area, centered on the middle of Tokyo. At the same time as theearthquake occurred, the vibration sensor shut-off mechanisms on the microprocessor-based gas
meters in users’ homes activated, resulting in an estimated 3 million gas meters from among a total ofabout 10 million such meters automatically shutting off the gas, ensuring the safety of our customers.
At the same time, SUPREME, which is located in the Tokyo Gas supply command center in ourhead office activated, collecting earthquake information from SI sensors installed on about 4,000
district supply governors and displaying the results of supply shutoff judgments in approximately fiveminutes (Fig.3). SUPREME quickly gathered enough information to enact policies guiding its initial
response by, in addition to earthquake information, collecting gas supply pressure information, electric
power failure information, and other detailed measured values for each district at the same time as itestimated damage to gas pipelines and evaluated the risk of liquefaction.
At fourteen of the approximately 4,000 district supply governors, shut off devices linked to SI
sensors shut off transmission of low pressure gas to maintain safety. Because eleven of these wereconnected to surrounding district supply governors by gas pipelines, supply was continued by backup
from adjoining district supply governors, but supply was stopped in districts supplied by three district
supply governors with independent networks unconnected to gas pipelines. And in Hitachi City,
maximum SI value of 70 kine was recorded, so supply to blocks was shut off based on supply
shutdown criterion. Supply was shut off to a total of 30,596 homes: 30,008 throughout Hitachi Cityand 588 in the other three districts. However, the safety of customers was ensured and secondary
disasters prevented by the rapid response led by SUPREME.

Fig.3 SI values observed by SI Sensors and Interpolated SI Values by 50m Meshes
3.2 State of damage to production and supply equipment
This earthquake did not damage important equipment which includes production equipment, gas
holders, and high pressure and medium pressure gas pipelines. To protect these important classes ofequipment, preventive measures described above were taken, and the effectiveness of these measures
was fully confirmed by this earthquake.
Low pressure gas pipelines with low earthquake resistance, which partially survived, were1511

damaged by the earthquake, but the number of cases of damage to gas pipelines buried underroadways is shown in Table 1, revealing that the total number of districts where supply continued anddistricts where supply was shut off was 230. According to damage estimations made by SUPREME(districts where supply continued) a total of 46 main pipelines and branch pipelines were damaged, aresult which conforms closely with the 61 actual damaged locations, confirming the effectiveness ofthe damage estimation equation intended to macroscopically clarify damage.
Liquefaction damage centered on the Urayasu District (outside of the Tokyo Gas supply region),
which was caused by this earthquake, also attracted considerable attention, but even in our supplyregion, liquefaction caused severe damage in the Mihama District of Chiba City. Supply to blocks was
not shut off, but it was difficult to perform repair work because of sand flowing into the inside of gaspipelines. The liquefaction risk estimation function of SUPREME calculated the PL value in 50m
mesh units, obtaining results shown in Fig.4, revealing trends generally similar to the actual state ofdamage on the scene, confirming the effectiveness of liquefaction estimation.
Table 1 State of Earthquake Damage by Equipment Category
Districts where gas supply Districts where gas supply
Equipment categorycontinued
shut off: Hitachi CityLNG Terminal
No damage
No damage
High/medium pressure pipelines
No damage
No damageLow pressure gas pipes
1520Main pipeline (diameter≧100m)
941
Branch pipeline (diameter＜100mm)
Service pipeline
1396※20030
Total damage to low pressure pipelines※Covers pipes buried under roads; excludes pipes on customers’ premises.

© 2011 ZENRIN CO., LTD. （Z11LE 第 226 号）

Fig.4 Estimation of Risk of Liquefaction by SUPREME and Actual Liquefaction Damage
3.3 Restoration to regions of 30,000 homes where supply was stopped
It was determined by the state of gas supply pressure after the earthquake that no gas pipelines
were damaged in regions where single gas pressure regulators automatically shut down by vibration
sensors cut off supply, one district in Yokohama, and 2 districts in Ibaraki Prefecture, and restoration

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was completed on March 11.
And to restore 30,008 homes in the Hitachi region, where seismic intensity of strong 6, or 70 kine
was observed by Tokyo Gas SI sensors, and where supply by all lifelines including electricity andwater were shut off, a total of 3,052 people including employees of Tokyo Gas, cooperating companies,and members of All Tokyo Gas took part in restoration work, first providing temporary supplies tohospitals and other priority supply customers, and succeeded in restoring the supply of gas to all
customers approximately one week after the earthquake.
Past management manuals have applied only to regions where, anticipating large-scale
earthquakes, gas pipeline damage would be severe, but in response to experience of the Niigata
Chuetsu Earthquake and the Chuetsu Offshore Earthquake, a restoration manual was revised andprepared last year to permit a response to various degrees of damage. Our ability to complete
restoration in a region where the supply to 30,000 users was cut off in only a week was a result of theapplication and skillful operation of this new manual.
The completion of restoration in the Hitachi Region was accompanied by the cancellation of thestate of emergency, and completion of the response by Tokyo Gas to the Great East Japan Earthquake
without any secondary disaster occurring.
4. FURTHER STRENGTHENING OF EARTHQUAKE PREVENTION MEASURES
Through its response to the Great East Japan Earthquake, Tokyo Gas confirmed the effectivenessof earthquake prevention measures based on the three types of measures—preventive measures,emergency measures, and restoration measures—and has shown that initial measures guided by
SUPREME functioned particularly well. On the other hand, this response did reveal a number ofproblems, and regarding the overall earthquake phenomenon, also confirmed extensive damage
exceeding past expectations in the form of giant tsunami and liquefaction.
To prepare for a giant earthquake which may occur tomorrow, Tokyo Gas will continue to improveits disaster prevention capability by tackling earthquake prevention measures even more resolutely,
and will strive to maintain and increase the public’s trust in its capabilities.

REFERENCES
1) Y. Shimizu, E. Ishida, R. Isoyama, F. Yamazaki, K. Koganemaru, W. Nakayama.(2003). “Building
a real time earthquake prevention system on a City Gas supply network and provision, analysis,
and use of wide-area ground information” Collected papers of the JSCE, No. 738/I-64, pp.
283-296.
2) E. Ishida, I. Suetomi, S. Yasuda, N. Hosokawa.(2009).”Proposal of an instantaneous estimation
method for liquefaction risk distribution for real-time earthquake prevention systems” Collected
papers on earthquake engineering of the JSCE, Vol. 30, pp. 596-605.
3) W. Inomata, Y. Norito.(2011).”Initial measures by Tokyo Gas to the Great East Japan Earthquake”
Proc. of the Eighth Conference on Earthquake Engineering in Japan, pp. 226-227.

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