Ocean Networks Canada - Bottom Pressure Recorder

Real-time tsunami data from the Tonga volcano

kshoemak@uvic.ca — Wed, 19 Jan 2022 20:29:04 +0000

Distance was no barrier to Ocean Networks Canada’s (ONC) capacity to provide real-time critical data about the tsunami risk following an underwater volcano eruption in Tonga on Saturday, 15 January 2022. Nine thousand kilometres from the volcano, the ONC offshore sensors gathered a variety of data, informing the National Oceanic and Atmospheric Administration’s Pacific Tsunami Warning Center alerts that go out to countries and territories in the Pacific and Caribbean regions.

This map of ONC's offshore NEPTUNE cabled networks shows arrival times of the tsunami waves caused by the Tonga volcano. Tsunami waves travel at ~800 kilometres per hour, the speed of a jet plane.

The tsunami’s eastward progress across the Pacific Ocean was tracked in real time by ONC’s bottom pressure recorders, using our sophisticated data management portal Oceans 2.0. This timely data provides critical ocean intelligence about wave heights, and informs official tsunami alerts to the public. Additional real-time wave height, ocean surface current and wind direction data are provided by high resolution coastal radars, including a state-of the art WERA over the horizon radar system in Tofino. These #knowtheocean data not only allow emergency services to activate safety protocols ahead of tsunami impacts, they also support future tsunami modelling and research.

Bottom pressure recorder data from ONC’s offshore NEPTUNE sensors show tsunami wave arrival times on Saturday, 15 January 2022.

“Tsunamis generated from undersea volcanos are rare, and measurements of the waves generated are even rarer,” says Kate Moran, president and CEO of ONC. “These data will be used to understand the risk of these types of ocean events.”

While the volcanic eruption in Tonga was not caused by an earthquake, the vibration registered the equivalent of an M5.8 quake on our seismic sensors.

Air pressure changes

Tonga's Hunga Tonga volcano just had one of the most violent volcano eruptions ever captured on satellite. pic.twitter.com/M2D2j52gNn
— US StormWatch (@US_Stormwatch) January 15, 2022

The shockwave caused by the violent Tonga volcano travelled around the globe three times and was reported around the world—as far away as the UK—producing changes in the barometric pressure for several minutes.

The volcano’s shockwave was recorded by ONC community observatories’ weather stations on the British Columbia coast. Notice the coincident blip shortly after 12.00.00 UTC at all locations.

Tsunami inundation studies

In addition to real-time monitoring, ONC supports tsunami resilience in at-risk coastal communities by integrating high resolution data and detailed geographic mapping into models for public safety.

This high-resolution land-river-sea digital elevation map (DEM) of the cross-border Salish Sea region reveals the complex geographic features that influence the behaviour of tsunami waves and currents as they move towards and impact the densely populated Vancouver lower mainland.

Since 2016, ONC has been involved with tsunami inundation and sea level rise studies for at-risk communities along the coast, including Port Alberni, Tofino, the Salish Sea, Prince Rupert, Haida Gwaii, and the Strathcona Regional District. In collaboration with government agencies, First Nations communities, and engineering companies, these projects inform local emergency planning efforts. Cutting edge science and engineering principles are coupled with Indigenous community engagement, seeking input from the local population and gathering historical knowledge of past tsunami events.

"We are grateful that our Strathcona Regional District coastlines did not experience any direct impacts of the Tonga tsunami, but it highlighted the critical value and urgency of the tsunami inundation project that is currently underway by Ocean Networks Canada and Northwest Hydraulic Consultants", comments Shaun Koopman, Strathcona Regional District Protective Services Coordinator.

This computer simulation of a local tsunami generated by a M9.0 Cascadia subduction zone megathrust earthquake shows the propagation of tsunami waves in Strathcona Regional District’s Esperanza Inlet and Nootka Sound on the northwest coast of Vancouver Island.

Like many regions on British Columbia’s coast, the Strathcona Regional District is considered highly vulnerable to tsunami events originating either from a large earthquake triggered in the Cascadia subduction zone offshore Vancouver Island, or one from the Alaska-Aleutian subduction zone to the north. ONC is currently working in partnership with local coastal engineering firm Northwest Hydraulic Consultants to support regional government, First Nations

“These tsunami inundation projects are a collaborative effort to understand which areas are most at risk, how soon the waves will impact the coast after an event, how high those waves may be and how fast we expect them to be moving,” says Gord Rees, ONC associate director, applied science solutions. “This information is crucial for identifying where the safety boundaries are, allowing emergency planners to work with their communities to ensure that appropriate emergency response plans are in place.”

Be tsunami prepared

Tsunamis are most often caused by undersea earthquakes that cause large waves. It may take hours for waves to reach the shore if an earthquake happens far away. Strong earthquakes near land could generate a tsunami that arrives onshore in less than 20 minutes.

A few sites for further information:

Listen to ONC President and CEO Kate Moran talk to CBC On the Island about the tsunami

Tsunami monitoring and public safety for at-risk communities

Magnitude 6.6 Earthquake

dwowens@uvic.ca — Thu, 24 Apr 2014 20:06:29 +0000

Multiple Ocean Networks Canada instruments recorded a magnitude 6.6 earthquake that struck beneath the seafloor off northern Vancouver Island at 8:10 PM (Pacific Daylight Time), 23 April 2014. Shaking from the earthquake was felt throughout Vancouver Island and by many people on the lower mainland in southwestern British Columbia.

Maps showing earthquake epicentre and aftershock locations (above, detail map shown above-right) and moderate to light shaking felt across northern Vancouver Island (lower map). The epicentre was 94 km south of Port Hardy, British Columbia and approximately 250 km north of NEPTUNE installations at Cascadia Basin. (Click to enlarge.)

Seismic Data

The main shock and numerous subsequent aftershocks were clearly recorded by seismometers at Cascadia Basin and Endeavour, as shown in data below. (Some of the smaller aftershocks shown in the seismic data from Endeavour may be associated with unrelated small local earthquakes that are frequently observed in this seismically active region.)

Earthquake initial shock and subsequent aftershocks recorded by the Cascadia Basin and Endeavour seismometers between 3:10-5:30AM, 24 April 2014 (UTC time) or 8:10-10:30 PM, 23 April 2014 (Pacific Daylight Time).

Bottom Pressure Recordings

Seafloor shaking was recorded by bottom pressure recorders at Cascadia Basin, Clayoquot Slope and Barkley Canyon shortly after the earthquake struck. However, there was no indication of a tsunami in the pressure data.

Seafloor pressure measured by bottom pressure recorders at three sites on the NEPTUNE Observatory. These recorders are situated at depths of 1285 m, 2706 m and 411 m. Pressure disturbances indicate seafloor shaking beginning approximately 3:11 AM, 24 April 2014 (UTC time) or 8:11 PM, 23 April 2014 Pacific Daylight Time).

Seafloor pressure anomalies (dBar) measured by bottom pressure recorders at three sites on the NEPTUNE Observatory. These recorders are situated at depths of 1285 m, 2706 m and 411 m. Blue lines show unfiltered wave height anomalies, while red lines are filtered to highlight longer-period waves such as tsunamis. Pressure disturbances indicate seafloor shaking (in blue) as the seismic waves passed, but there was no subsequent indication of a tsunami in the pressure data.

Ocean Networks Canada instruments on (and in) the seabed of the Fraser River Delta also registered the shaking, providing scientists at Natural Resources Canada information on how the delta sediments, and pressures within, respond to large earthquakes. An unproven, but commonplace, perception is that earthquakes could cause failure on the delta; Natural Resources Canada scientists are testing this hypothesis.

Rumbles and Crackles

The sound of the earthquake was recorded by Ocean Networks Canada's low-frequency hydrophone in Cascadia Basin, approximately 250 km away from the epicentre. The noise generated was so loud it saturated the hydrophone input. The spectrogram and audio recording of the earthquake are shown below. This recording has been sped up 400% to make the earthquake audible. The crackling sounds were caused when the hydrophone sensor was saturated.

Strike-slip Earthquakes

Seismologist analyses and the absence of a tsunami suggest that this earthquake likely occured on a strike-slip (lateral) fault. Vertical displacement for strike-slip earthquakes is typically much less than may be expected from a major subduction earthquake. The following short video illustrates the distinction between strike-slip and subduction earthquakes.

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.”

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

Haida Gwaii Earthquake and Tsunami

rlat@uvic.ca — Sat, 27 Oct 2012 07:00:00 +0000

A powerful magnitude 7.7 earthquake struck central Moresby Island in the Haida Gwaii archipelago at 8:04PM PDT, 27 October 2012. Residents along the west coast—from Alaska to Vancouver—also felt several aftershocks up to magnitude 5.8. However, no major damage or injuries were reported. This was the largest temblor to hit Canada since 1949, when an 8.1-magnitude quake hit west of the Queen Charlotte Islands, in the same area.

The following plots show both seismic and bottom pressure data collected by Ocean Networks Canada instrumentation, located approximately 600 km south of the earthquake epicenter. The light-blue plots at upper-left illustrate changes in pressure, as measured by bottom pressure recorders at four node locations. In the top three plots, initial strong blue signatures, beginning at 3:04 UTC, indicate shaking of the seafloor as seismic energy passed through the region. As this energy dispersed, the recordings indicate changes in sea level above each bottom pressure recorder as waves emanating from the disturbance traveled across the ocean's surface. The fourth plot shows bottom pressure anomalies at Folger Passage, a shallow (100 m) near-shore station where surface swell typically conceals tsunami waves from easy detection by the casual viewer.

The lower five plots, in dark blue above, illustrate seismic energy as measured by four Ocean Networks Canada seafloor seismometers and one land-based seismometer located in Bella Bella on British Columbia's central coast. Earthquake onset is clearly indicated in all five plots, with Bella Bella recording the earliest onset, because it is located much closer to the earthquake epicenter, 265 km to the southeast. The Bella Bella seismometer is part of the Canadian National Seismograph Network, maintained by National Resources Canada's Pacific Geoscience Centre.

Numerous aftershocks were also detected following the initial earthquake, with over 50 magnitude 4+ aftershocks recorded in the initial 16 hours. Most of these aftershocks occurred beneath the seafloor, as indicated in the following USGS map.

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, northern-most island in the Haida Gwaii archipelago, measured 69 cm. Tsunami wave heights as high as 76 cm were recorded in Kahului, Maui, HI, and harbour oscillations up to 1.2 m were measured in Hilo, HI.

The tsunami generated by this earthquake was not nearly as large and devastating as those struck Sri Lanka, Indonesia and Japan in recent years, because it occurred on a strike-slip (lateral) fault. Vertical displacement for strike-slip earthquakes is typically much less than may be expected from a major subduction earthquake. The following short video illustrates the distinction between strike-slip and subduction earthquakes.

For scientists like those at the Pacific Geoscience Centre and other institutions studying tsunami propagation in the northeast Pacific, this event will provide valuable insights. The tsunami generated by this earthquake was similar in size to other tsunamis, such as last year's Japan tsunami and the Chilean tsunami of February 2010, when they reached the northeast Pacific. Although tremendously large in their source regions, these tsunamis diminished significantly after crossing large ocean basins to reach coastal British Columbia. The Haida Gwaii tsunami is the first regional tsunami tracked by Ocean Networks Canada's sensor network; its local source region is expected to result in different wave responses in BC's coastal embayments. By comparing these two types of tsunamis (distant vs. local), scientists can begin to piece together a picture of how BC coastal zones may react to large tsunamis originating in this region.

Samoan Tsunami Detected

rlat@uvic.ca — Tue, 20 Oct 2009 07:00:00 +0000

When a devastating magnitude 8.0 earthquake occurred roughly 200 km south of the Samoan Islands at 17:48:11 UTC on Tuesday September 29, 2009, it generated a trans-oceanic tsunami that spread at jet-like speeds throughout the Pacific Ocean.

At 04:57:33 UTC on 30 September, roughly 11 hours after the earthquake, five of our newly deployed Bottom Pressure Recorders (BPRs) and one pressure sensor installed at the ODP 1027 (Cascadia Basin) CORK began recording the leading waves from this event (click map below to see BPR locations). Capable of resolving sea level displacements as small as 1/10th of a millimeter, the BPRs installed within 15 km of our Cascadia Basin location as part of the NEPTUNE “tsunami meter” provided Canadian researchers with amazingly clean recordings of the tsunami signal as the waves passed over the 2700 m deep Cascadia Basin off the west coast of Vancouver Island. Similar, but somewhat noisier tsunami signals were subsequently observed up to 50 minutes later by BPRs at continental margin sites Clayoquot Slope, Barkley Canyon, and Folger Passage.

The high resolution NEPTUNE tsunami meter recorded a series of four well defined primary waves (click image below) with decreasing times between successive wave crests of 12 min 50 s, 10 min 54 s, and 9 min 54 s, indicative of wave dispersion effects. Trough-to-crest heights of the primary waves were typically around 4 cm but reached a maximum height of 5 cm during passage of the third wave in the wave train. Wave heights diminished to around 2-3 cm after the leading group had propagated through the array. The tsunami continued to be recorded for the next few days as waves from the event rebounded around in the Pacific basin.

Continuing shoreward, the tsunami waves amplified to around 10-20cm as they crossed the continental shelf and progressed into embayments along the British Columbia coast. Observed wave heights at coastal tide gauges were around 15cm at Bamfield and Tofino, 18cm at Port Alberni, 8cm at Victoria, and 18cm at Henslung on Langara Island in the northern Queen Charlottes. Wave periods in the coastal regions were spread over a range of 5 to 25 minutes owing, in part, to local resonance effects.

Deep ocean data records like these are invaluable for refining models that predict tsunami hazards in coastal areas and for providing early warning assessments. The only negative aspect of our highly successful Samoan tsunami measurements was the greatly reduced capacity of our high resolution tsunami “antenna” in Cascadia Basin due to the missing third (northeastward tending) arm of the array. Weather and technical glitches prevented its deployment this summer. Because the tsunami originated to the southwest, data from the northeast BPR would have greatly increased our ability to accurately define the directionality and transformations of the tsunami waves as they propagated toward the coast. Deployment of the third arm in 2010 will be critical to the long-term success of the Ocean Networks Canada long-wave BPR array.

Learn more

The above story provided by the NEPTUNE Canada tsunami team: R.E. Thomson (1), M. Heesemann (2), S.M. Mihaly (1), E.E. Davis (2), J. Cherniawsky (1), A.B. Rabinovich (1), and I.V. Fine (1).

Fisheries and Oceans Canada, Institute of Ocean Sciences, Sidney, B.C.
Natural Resources Canada, Pacific Geosciences Centre, Sidney, B.C.

Ocean Networks Canada - Bottom Pressure Recorder

Real-time tsunami data from the Tonga volcano

Air pressure changes

Tsunami inundation studies

Be tsunami prepared

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Magnitude 6.6 Earthquake

Seismic Data

Bottom Pressure Recordings

Rumbles and Crackles

Strike-slip Earthquakes

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Haida Gwaii Quake Monitored by NEPTUNE Canada

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Haida Gwaii Earthquake and Tsunami

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Samoan Tsunami Detected

Learn more

The above story provided by the NEPTUNE Canada tsunami team: R.E. Thomson (1), M. Heesemann (2), S.M. Mihaly (1), E.E. Davis (2), J. Cherniawsky (1), A.B. Rabinovich (1), and I.V. Fine (1).

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