INNOVATION March-April 2016

f ea t ures earth’s crust, was less than 80 kilometres from Site #7, in the Lower Mainland, and about 420 kilometres from Site #19, north of Kamloops. The seismogram from Site #19 shows the earthquake’s P-wave arrived there at about 87 seconds and the S wave arrived at about 127 seconds— providing a 40-second advance warning. However, the Site #7 system detected the P-wave about 45 seconds before it arrived at Site #19. Allowing one second for communications-system delay, the combined systems extended the practical advance warning of the S-wave’s arrival at Site #19 to about 83 seconds. Had the S-wave’s predicted intensity presented a threat to facilities near Site #19, the extended advance warning would have provided time for personnel to evacuate. In addition to triggering facility alarms, the system would have notified clients via mobile app. It would have also automatically shut down production equipment and gas, water and electricity intakes, triggered start-up of stand- by generators, and notified emergency first responders. even 100 schools, the systems’ cost becomes a concern. A device made of strong motion detectors and designed by University of British Columbia (UBC) engineers a few years ago provides cash-constrained school districts with a basic solution. The systems—developed by civil engineers at the UBC’s Earthquake Engineering Research Facility—use off-the-shelf accelerometers that cost pennies each, detect vibrations and measure ground motion. Large numbers of low-cost accelerometers are assembled and configured to optimise the quality and sensitivity of the motion signals detected and measured. As with most early earthquake warning systems, the devices designed for schools are calibrated to detect earthquakes’ compression (P) waves, which children may not notice and adults may ignore. Fast-moving P-waves, which rarely damage structures, may be mistaken for the rumbling of a heavy truck nearby. They precede a quake’s slower, damaging shear (S) waves—by just a few seconds or as many as tens of seconds, depending how far away the earthquake’s ground zero is. Encased in plastic cylinders, the school devices are usually buried in pairs—each about 30 metres apart from its partner—and about two metres deep in a schoolyard. They connect to black boxes in the schools, and relay signals and measurements to powerful servers at UBC, where software monitors and analyses them. The system is calibrated to recognise and disregard tremors caused by construction, transport trucks or school Low-Cost Earthquake Warning System Alerts Schools British Columbia’s south coast school districts are responsible for hundreds of schools and for the safety of students, faculty and staff learning and working within them. Although early earthquake warning systems have been around for years, when a school board seeks to install the systems in dozens or

The December 29 event demonstrates the dual use of on-site earthquake warning systems. They reduce seismic risk for critical facilities and collect continuous, regional seismic data for use in research. Experience in BC over several years has shown that, although we cannot predict precisely when earthquakes will occur, well-designed and integrated earthquake early warning systems can provide enough warning of an imminent earthquake to reliably and cost-effectively reduce risk to the public and to infrastructure. v Dr. Iain Weir-Jones, P.Eng., FGS, and Dr. Anton Zaicenco, P.Eng., are respectively Chief Technology Officer and Chief Seismologist at Weir-Jones Engineering Consultants Ltd., in Vancouver, BC. The company designs autonomous systems that collect and analyse real-time data for clients around the world.

buses. In actual earthquakes, it triggers alarms in the schools. This occurs within milliseconds and gives children, teachers and staff seconds to seek shelter beneath desks or in designated safe areas before the damaging S-wave arrives. Earthquake Engineering Research Facility Director Dr. Carlos Ventura, P.Eng., presented information about the earthquake early warning system already implemented and operational in the province to the BC Liberal caucus and Opposition leaders during APEGBC’s recent meetings with the provincial government (see page 9).

Large numbers of off-the-shelf accelerometers are assembled and configured to detect and measure

vibrations and ground motion.

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