Ocean Networks Canada - Seismic Data

Tsunami alert follows 8.2 quake off Chile

dwowens@uvic.ca — Wed, 02 Apr 2014 04:25:42 +0000

On April 1 at 4:46:45 PM Pacific Daylight Time (23:46:45 UTC), a magnitude 8.2 earthquake occurred off Chile's Pacific coastline, according to the US Geological Survey. Ocean Networks Canada instrumenatation captured both ground shaking and a very small tsunami as they crossed the northeast Pacific.

Map of the epicentre and 16 aftershocks along the subduction zone between the Nazsca and South American plates, 1 April 2014. Data provided by USGS and plotted using Google Earth. (Click to enlarge.)

At a depth of 20.0 km below the seabed, the shallow near-field quake struck 86 km northwest of the mining area of Iquique, hitting a region that has been rocked by numerous quakes over the past two weeks. According to the USGS, this earthquake occurred as the result of thrust faulting at shallow depths near the Chilean coast. The location and mechanism of the earthquake are consistent with slip on the primary plate boundary interface, or megathrust, between the Nazca and South America plates. In this area, the Nazca plate subducts eastward beneath the South America plate at a rate of 65 mm/yr. Subduction along the Peru-Chile Trench to the west of Chile has generated the uplift of the Andes mountain range.

Ocean Networks Canada's seismometer in Cascadia Basin recorded the tremors as they crossed the North Pacific. Seismic data clearly indicate arrival of the initial P waves approximately 750 seconds (12.5 minutes) after the earthquake, and following S waves about 1375 seconds (23 minutes) after the earthquake struck. Bottom Pressure Recorders on the NEPTUNE Observatory also detected passage of the tsunami in real time, as it crosses our observing stations in the northeast Pacific.

Data from the Cascadia Basin ocean-bottom seismometer indicating arrival of P and S waves. The top trace shows East-West motions, the centre trace shows North-South motions, and the lower trace shows vertical motions. (Click to enlarge.)

A 1.9-metre tsunami was recorded at a northern Chilean port Tuesday evening. The Pacific Tsunami Warning Center issued an alert for all of Latin America's Pacific coast. There was no threat issued to the Pacific coast along North America.

NOAA issued a forecast of tsunami heights as the energy propagated away from the source region, indicating heights up to 100 cm close to the epicenter, with rays of 2-10 cm wave heights extending across portions of the South Pacific Ocean toward New Zealand and archipelegos in the South-Central Pacific.

Tsunami wave energy propagation forecast issued by the Pacific Tsunami Warning Center, showing contours of maximum wave amplitudes (in cm) associated with the 1 April 2014 earthquake.

Travel times for tsunami propagation were also modeled by the National Tsunami Warning Center, with expected arrival of a small (2-4 cm) tsunami in coastal British Columbia beginning 15 hours after the event, around 7:00 AM Pacific Daylight Time.

Predicted travel times for tsunami waves generated by the 1 April 2014 earthquake. Three-hour intervals are marked by the heavy white lines, intermediary hours are marked by blue shades and dashed white lines indicate half-hour boundaries. Arrival in both New Zealand and British Columbia was predicted to begin approximately 15 hours after the initial earthquake.

Seafloor pressure traces from the CORK pressure instrument at Cascadia Basin, 1-2 April 2014. The upper plot shows initial passage of the earthquake just past 00 UTC (indicated by the blue lines), followed by passage of the small tsunami beginning at 14 UTC. The lower plot focuses on the tsunami onset period, 11-15:20 UTC. Wave amplitudes at this deep-water site (2660 m) were approximately 8 mm.

No stranger to seismic activity, Chile is one of the world¹s most earthquake-pronecountries. In 2010, a magnitude-8.8 quake and ensuing tsunami in central Chile killed more than 500 people and destroyed several hundred thousand homes along the coast.

Haida Gwaii Quake Monitored by NEPTUNE Canada

rlat@uvic.ca — Sun, 28 Oct 2012 07:00:00 +0000

Just after 8 pm on October 27, a magnitude 7.7 earthquake struck off the coast of BC, at a depth of 17 kilometres and centred 139 km south of Masset in the Haida Gwaii region.

Residents along the west coast—from Alaska to the lower mainland—also felt numerous aftershocks up to magnitude 5.8. No major damage or injuries have been reported.

Although similar in size to the earthquakes in Japan (2011) and Chile (2010) this event represents the first regional tsunami tracked by the NEPTUNE observatory.

"Ocean Networks Canada sensors at various locations and depths are designed to register and monitor these events, that are caused by a buildup of stresses in the earth’s crust," said Dr. Martin Heeseman, earthquake dynamics specialist with the Ocean Networks Canada Observatory. "Seismographs monitored the ground motion caused by these quakes, while bottom pressure recorders and the CORK pressure sensor measured the long (tsunami) waves that crossed over the 800 km cabled seafloor network."

These highly specialized, ultra-sensitive instruments provide real-time data that may provide vital information for emergency organizations and coastal residents.

The data from this earthquake, a sample of which is given above, is unique for the study of near-field tsunamis. “This is the first time we have data from our offshore stations to test the models and response of the coast to these near-field waves,” said Dr Steve Milhaly, Ocean Networks Canada's specialist in ocean/climate dynamics. “It’s these locally generated tsunami waves that will be the devastating ones for our coastal regions.”

Tsunami warnings originally issued for a large stretch of the North and Central coast, as well as the Haida Gwaii region and eastward to Hawaii, were later cancelled or downgraded. One wave that hit Langara Island, in the Haida Gwaii area, measured 69 centimetres.

This was the largest tremblor to hit Canada since 1949, when an 8.1-magnitude quake hit west of the Queen Charlotte Islands, in the same area. In January 1700, a 9.0-magnitude earthquake struck offshore of Vancouver Island.

For more information, visit the extended news release: Haida Gwaii Earthquake and Tsunami

Chilean Earthquake and Tsunami

rlat@uvic.ca — Thu, 04 Mar 2010 08:00:00 +0000

Major Earthquake

On Saturday, Feb. 27 2010, 0634UTC, a magnitude 8.8 earthquake occurred off the coast of Chile. A tsunami advisory was issued for the BC coast. According to the USGS, "this earthquake occurred at the boundary between the Nazca and South American tectonic plates. The two plates are converging at a rate of 70 mm per year. The earthquake occurred as thrust-faulting on the interface between the two plates, with the Nazca plate moving down and landward below the South American plate."

With a magnitude of 8.8, this recent earthquake was the seventh strongest ever recorded, and 500 times stronger than the magnitude 7.0 earthquake that struck Haiti in January 2010. The most powerful earthquake ever recorded, (magnitude 9.5) also occurred off the coast of Chile in this region, the Valdivia earthquake of May 1960.

Seismic Monitoring

Three Ocean Networks Canada broadband seismometers, which lie buried in seafloor sediments at our Barkley Canyon, Cascadia Basin and Clayoquot Slope locations, recorded the earthquake. The tremor accelerations were also recorded by the gravimeter in our Seafloor Compliance System at Clayoquot Slope.

Tracking the Tsunami

Within an hour of the earthquake, tsunami waves over 5m in height struck coastal Chile, leading to the deaths of hundreds of people. Tsunami waves ranging 1-5m were observed in many locations, including New Zealand, French Polynesia and Hawaii. The tsunami propagated across the Pacific at jet-like speeds and reached coastal British Columbia by 23:00UTC, 16.5 hours after the event. Tsunami wave heights of 50 to 100cm were recorded along the West Coast of Vancouver Island.

Scientists at Canada's DFO Institute of Ocean Science fed data from one of the Ocean Networks Canada bottom pressure recorders into their regional tsunami model for this event, allowing them to simulate wave motions and interactions for coastal British Columbia, including the Strait of Georgia.

Data from events like these are an invaluable aid to scientists, who are working to improve tsunami prediction models for the West Coast. In the future, improved models could greatly benefit emergency response, public safety and disaster-preparedness operations.

Ocean Networks Canada - Seismic Data

Tsunami alert follows 8.2 quake off Chile

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Haida Gwaii Quake Monitored by NEPTUNE Canada

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Chilean Earthquake and Tsunami

Major Earthquake

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Tracking the Tsunami

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