Early earthquake warning system for city gas network

Tokyo Gas supplies city gas to 8 million customers around Tokyo metropolitan area and has social responsibility to secure safety even after big earthquake. To prevent gas-caused secondary disaster after earthquake, it is necessary to make prompt and reasonable decision. For this purpose, SIGNAL (Seismic Information Gathering Network Alert System) has been developed to support to make decision and has been in operation since June, 1994. One of SIGNAL's function is quick monitoring SI readings and seismic acceleration at 331 locations, acceleration waves at 5 locations and rising ground water levels at 20 locations considered most at risk from ground liquefaction, using a reliable radio network. This real-time earthquake data is linked to data bases of gas pipelines and ground conditions to give an accurate damage assessment, based on pipe damage experiences suffered in previous earthquakes. The assessment of damage to the gas network is useful for the rapid implementation of emergency work and in drawing up efficient and accurate restoration plans.