Building an Improved Underwater Earthquake Monitoring Network

By Chantal Hunter
January 2012

Researchers with the SeaJade project are building a seismographic network in order to better understand how and why earthquakes are produced.

In March 2011, a magnitude 9.0 subduction earthquake struck the northeastern coastal region of Japan. Though damage was widespread from the earthquake and resulting tsunami, it was significantly lessened due to monitoring and data analysis that helped prepare citizens for such events.

SeaJade researchers deploying seismology instruments

Along the same lines, scientists from Natural Resources Canada’s (NRCan’s) Geological Survey of Canada (GSC) are collaborating with their Japanese and U.S. counterparts to deploy a dense seismic network on the seafloor off the west coast of North America. They hope that they can use data from the new network to develop more accurate earthquake hazard models of the region that will help protect people living close to a major underwater subduction zone.

About Subduction Zones and Earthquakes

Subduction zones are areas where one tectonic plate is pushed beneath another. Large sections of the subduction fault can get stuck for hundreds of years and then suddenly slip. During a slip, the stored-up energy is suddenly released, causing an earthquake. The results can in some cases be very severe, as is the case with the recent magnitude 9.0 event in Japan. 

While seismic activity in North America is less frequent compared with Japan, the subduction fault off the North American west coast also generates earthquakes of a similar magnitude. The monitoring network being deployed there is the first attempt to gather the detailed offshore data that is needed to guide preparation for a future large magnitude earthquake.  

Collaborative Research

Japanese researchers preparing Ocean Bottom Seismometers

Dubbed SeaJade, the Seafloor Earthquake Array — Japan–Canada Cascadia Experiment is a multi-year project involving researchers from NRCan’s Geological Survey of Canada (GSC), the Japan Agency for Marine-Earth Science and Technology (JAMSTEC), the University of Victoria and the Woods Hole Oceanographic Institution (WHOI).

SeaJade researchers are deploying a short-term deep-water seismic monitoring network along the west coast of Vancouver Island. Using the network data, they are conducting studies to get an improved image of the subduction zone. The goal is to better understand how and why earthquakes are produced in order to be better prepared when they do occur.

The first phase of the project involved the deployment of 32 short-period Ocean Bottom Seismometers (OBSs) and 10 broadband instruments to accompany two permanent NEPTUNE Canada broadband seismometers. Early results are consistent with independent GPS data that show the subduction zone is fully locked and building strain toward the next large earthquake, which is expected to have a magnitude similar to the magnitude 9.0 earthquake in Japan.

Mitigating Risk in British Columbia

The last subduction earthquake off Canada’s west coast occurred in 1700 and, at magnitude 9.0, ruptured the offshore subduction fault from Vancouver Island, B.C., all the way to northern California. Kelin Wang, a GSC scientist working on the SeaJade project, hopes that with enhanced monitoring and continued research, earthquakes of this nature will become a more manageable risk.

“We continue to study earthquakes in order to better understand the seismic risks,” says Kelin. “While the exact timing of an earthquake cannot be predicted, understanding the earthquake process and hazards can help minimize the risk to humans as well as greatly reduce economic losses.”

If you found this article interesting, you may want to read:

• Underwater Sensors Improve Earthquake Monitoring
• Preparing for Earthquakes

To read about related articles, see Natural Hazards

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