Strong Motion network
NetQuakes, Dense Instrumentation in Urban Areas
Any country as large as the USA faces difficult choices within its earthquake monitoring strategy. Striking the right balance between the possibility of a large earthquake in a remote area causing little disruption and a smaller earthquake in a densely populated causing massive damage has to be a risk very carefully managed.
A current area of significant risk has been identified as surrounding the San Francisco East Bay and the Hayward fault areas. The USGS is trying to achieve a denser and more uniform seismograph spacing in the Bay Area to provide better measurements of ground motion during earthquakes. To do this, the NetQuakes instruments are deployed that communicate their data to the USGS via the Internet. These instruments connect to an existing local network using WiFi and use existing Broadband connections to transmit data after an earthquake.
On 6 Jun 2009 a 3.1 earthquake rattled the East Bay but there were no immediate reports of injury or damage. Scientists then probed the Lucas Valley for earthquake clues as the one almost certain thing around the East Bay area is that something bigger now appears to be looming. On 25 Jun 2009 the USGS described the Hayward fault as ‘a tectonic time bomb, due anytime for another magnitude 6.8 to 7.0 earthquake and that the coming Hayward fault earthquake will probably kill hundreds of people and cause damage worth perhaps $100 billion ‘. This locality has therefore been identified as an area where the precise seismic risk of earthquake is not yet fully understood.
New instrumentation has been sought to monitor this emerging situation and included finding suitable locations within built up areas to accept and install earthquake monitoring systems. The NetQuakes seismographs specification requires access the Internet via a wireless router connected to an existing Broadband Internet connection. The seismograph then transmits data to the USGS only after earthquakes above the magnitude of around 3, but will not consume any significant bandwidth and should require only minimal maintenance.
While enhancing the Strong Motion Network coverage in this seismically high-risk area, the measurements improve also the ability to make rapid post-earthquake assessments of expected damage and contribute to the continuing development of engineering standards for construction projects. They may well also shape future requirements within other urban areas over a longer time period.
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