October 31, 2013
Earthquake Prone Regions Could Benefit From Updated Warning System
redOrbit Staff & Wire Reports - Your Universe Online
Relocating some of the seismic stations in California and upgrading earthquake-detection technology could improve early warning systems throughout the state, according to new research appearing in the November edition of the the journal Seismological Research Letters.The effect would be particularly noticeable in regions that are poorly served by the current network, explained Serdar Kuyuk, assistant professor of civil engineering at Sakarya University in Turkey who completed the research while serving as a post-doctoral fellow at the University of California-Berkeley.
Those areas include the region south of the San Francisco Bay Area down to northern Los Angeles, as well as north of the Bay Area, said Kuyuk and co-author Richard Allen, director of the Seismological Laboratory at UC-Berkeley. While the US Geological Survey (USGS)/Caltech Southern California Seismic and TriNet Network in Southern California was upgraded following the 1994 Northridge earthquake, the researchers believe that more effort needs to be made to develop a fully-functional earthquake early warning (EEW) system.
“We know where most active faults are in California, and we can smartly place seismic stations to optimize the network,” Kuyuk said in a statement Wednesday, adding that California recently passed a law calling for the creation of a statewide EEW system. “We should not wait until another major quake before improving the early warning system… the study is timely and highlights for policymakers where to deploy stations for optimal coverage.”
EEW systems detect the early stages of an earthquake and issue cautionary alerts of potential seismic activity, the study authors explained. The plan proposed by Kuyuk and Allen would allow the maximum amount of warning time for seismic activities, while also reducing the number of so-called blind spots (regions that currently receive no early notification of potential earthquakes) and also taking budget considerations into account.
“Seismic stations detect the energy from the compressional P-wave first, followed by the shear and surface waves, which cause the intense shaking and most damage,” the Seismological Society of America said in a statement. “The warning time that any system generates depends on many factors, with the most important being the proximity of seismic stations to the earthquake epicenter. Once an alert is sent, the amount of warning time is a function of distance from the epicenter, where more distant locations receive more time.”
The blind zones, which exist between the Bay Area and Los Angeles (where there are active faults) do not currently receive any warning prior to the arrival of more damaging S-Waves, the researchers said. Only 10 stations exist along the 150-mile region of the San Andreas Fault, and by adding more stations, it would maximize the number of people who would be forewarned of earthquakes before they occur in these regions.
However, Allen cautions that adding new stations will not necessarily be an easy task. “While there is increasing enthusiasm from state and federal legislators to build the earthquake early warning system that the public wants, the reality of the USGS budget for the earthquake program means that it is becoming impossible to maintain the functionality of the existing network operated by the USGS and the universities,” he explained.
“The USGS was recently forced to downgrade the telemetry of 58 of the stations in the San Francisco Bay Area in order to reduce costs,” Allen, whose research was funded by the USGS and the Gordon and Betty Moore Foundation, added. “While our SRL paper talks about where additional stations are needed in California to build a warning system, we are unfortunately losing stations.”
According to Kuyuk and Allen, six miles is the ideal distance between seismic stations in regions located along major fault lines or near large urban centers, while in other regions, a distance of 12 miles between stations would provide adequate warning. They believe that their goals of increased station density and wider coverage area could be accomplished by upgrading technology used in the existing facilities, integrating Nevada stations into the current network, relocating some existing stations and adding new ones to the network.
Separate research, also appearing in SRL, suggests that using inexpensive MEMS accelerometers – tiny sensors used in smartphones and laptops that have been shown to effectively detect ground motion – could be used to construct a low-cost, high density seismic network to serve as an EEW system for Taiwan.
In his study, Yih-Min Wu, of National Taiwan University, explained that such a system would reduce the time between the occurrence of an earthquake and the issuing of a first alert, essentially upping the potential warning time. Currently, Taiwan’s EEW system consists of 109 seismic stations capable of issuing alerts within 20 seconds of first detecting seismic activity.
Image Below: This is a map of the blind-zone radius for California. Yellow and orange colors correspond to regions with small blind zones and red and dark-red colors correspond to regions with large blind zones. Credit: SRL