Ocean Networks Canada - alaska

Resilience through preparedness: remembering the 1964 ‘Good Friday’ tsunami

duncanlowrie@uvic.ca — Wed, 08 Apr 2020 21:15:41 +0000

56 years ago, the ‘Good Friday’ earthquake rocked the Gulf of Alaska, causing a major tsunami to roll across the Pacific Ring of Fire on the evening of 27 March 1964. Few in Tofino were aware of the magnitude 9.2 earthquake or the alerts being sent by the US tsunami warning centre. Three and a half hours after the shaking, a series of tsunami waves swept over beaches and strong currents scoured the Pacific northwest coastline (Figure 1). Being early springtime and late at night in a sparsely populated Tofino, the area suffered no fatalities or injuries and only minor damage was reported. The event was a wake-up call for a risk that was not well understood nor well prepared for.

Figure 1. The 1964 earthquake off the coast of Alaska caused multiple tsunami waves to funnel up the narrow Port Alberni Inlet. There were no casualties, but the disaster damaged buildings, downed phone and power lines, and had a lasting impact on the community. Photo credit: Charles Tebby, Alberni Valley Museum.

Today Ocean Networks Canada (ONC) is helping to build resilience in Tofino—and elsewhere in British Columbia—by integrating the latest science and technology into tsunami planning efforts and improving awareness of the risk. Local leaders are partnering with scientists, engineers and tsunami experts to integrate local hazard models, community risk assessments, and tsunami mitigation best practices, to prepare for the next big one. Tofino’s Tsunami Mitigation Plan outlines actionable strategies for decreasing the risks associated with this threat. As a direct result, Tofino has improved understanding of the tsunami risk and what to do to better prepare (Figure 2).

Figure 2. Left: As part of Tofino’s Tsunami Mitigation Plan, the remote Pacific Rim municipality has developed a Tsunami Evacuation Route (left), with a map and information about emergency preparedness for residents and visitors. Right: Installed at Tofino airport in 2015, ONC’s WERA (WavE RAdar) high frequency oceanographic radar array is a shore-based remote sensing system that includes four transmitting and 12 receiving antennas that monitor ocean current speed in real-time.

The future is in real-time. In our highly connected world, tsunami information can be rapidly disseminated across a broad range of communication technologies. For example, technological advances include using high frequency radar to continuously monitor ocean surface levels. Coastal radar, including the WERA radar located at Tofino’s Long Beach Airport, delivers real-time ocean wave height data that can be used for tsunami response decisions and situational awareness (Figure 3).

Figure 3. In October 2016, ONC’s high frequency oceanography WERA radar system provided Tofino with real-time data when Typhoon Songda triggered a tsunami alert. “Real-time data from an instrument like the WERA radar supports critical and lifesaving decision making for coastal communities,” commented Keith Orchiston, Tofino’s Emergency Program Coordinator at that time.

On a broad scale, ONC uses real-time observations of earthquake shaking and tsunami wave heights to support official tsunami alerts and better monitor the tsunami threat. ONC’s Applied Science team uses detailed digital elevation maps and runs tsunami models on high powered computers which inform plans for future tsunamis. Public education on the science of tsunami and public safety best practices support an awareness of the risk and helps people take action to decrease their level of risk. Together, we are moving resilience forward.

Taking appropriate action is key, which is why ONC supports earthquake and tsunami preparedness education and training such as the High Ground Hike tsunami preparedness initiative, Masters of Disasters education program and Great BC ShakeOut earthquake drill.

In a disaster, we’re all in it together. What we do today will influence the outcomes of our next major tsunami event. At ONC, we are doing our part to help coastal communities prepare and become more resilient.

Data from Alaska’s Magnitude 7.9 Earthquake and Tsunami

kshoemak@uvic.ca — Tue, 23 Jan 2018 19:23:39 +0000

On 23 January 2018, a magnitude 7.9 earthquake occurred in the Gulf of Alaska at 1:35 am PT. A tsunami warning was issued for the west coast of Canada and the United States. The tsunami warning was cancelled at 4:40 am PT.

Ocean Networks Canada’s (ONC) real-time sensors detected the earthquake and the subsequent small tsunami that rippled out across the northeast Pacific (Figure 1).

Figure 1. The relative timing of the magnitude 7.9 Alaskan earthquake and the subsequent small tsunami as detected by ONC real-time sensors.

The resulting tsunami wave was relatively small because this was a strike-slip earthquake characterized by side-to-side motion, which displaces less water than the vertical motion of a subduction zone earthquake.

This morning's 7.9 earthquake occurred along a strike-slip fault. The horizontal movement of the two plates in a strike-slip fault, typically limits the threat of tsunami's pic.twitter.com/o7kgwNHqxS
— Greg Diamond (@gdimeweather) January 23, 2018

the Alaska earthquake generated a small tsunami detected by @Ocean_Networks sensors off Canada's westcoast #tsunami pic.twitter.com/MK0K0SLOi8
— Kate Moran (@katemoran) January 23, 2018

Alaska #tsunami just passed @Ocean_Networks bottom pressure station at Clayoquot Slope: 3-cm sea level drop; not big but there.https://t.co/b27CdUo3as pic.twitter.com/T6A8FT2SdT
— Martin Scherwath (@mscherwath) January 23, 2018

Friday 26 January is the anniversary of the last big Cascadia subduction zone earthquake that occurred in 1700, with an estimated magnitude of 8.7-9.2, which caused a widespread tsunami that devastated coastal Japan (Figure 2).

Figure 2. Modeled tsunami caused by the 26 January 1700 megathrust earthquake. Image courtesy of Kenji Satake.

This close call presents a perfect opportunity for British Columbians to become better prepared. Know the risks, have a plan, get a kit - these are the three major components of preparedness. Get started with help from Prepared BC (Figure 3).

Figure 3. Are you prepared for an emergency?

ONC’s earthquake and tsunami technology, research, data, modelling, and alert systems are being developed in collaboration with partners from government, science, academia, and industry in Canada, the United States, and around the world.

Negligible Tsunami From Alaska Earthquake

dwowens@uvic.ca — Sat, 05 Jan 2013 08:00:00 +0000

A strong magnitude 7.5 earthquake struck west of Craig, Alaska at 12:58AM PST, 5 January 2013. Tsunami warning and alerts were issued for a broad section of the Alaskan and Canadian coastline, but no damaging waves were generated. According to the USGS, this earthquake was likely "related to that Haida Gwaii earthquake three months previously, and is an expression of deformation along the same plate boundary system."

The following plots show tide data from Port Alexander, AK (upper-right) and pressure data (lower-left) from Ocean Networks Canada CORK and bottom pressure recorder instruments at three stations on our network. Tide data indicate a crest-to-trough wave amplitudes of 20-30 cm at Port Alexander, with the initial waves arriving 41 minutes after the earthquake. The pressure plots show strong shaking at the seafloor (indicated by the blue areas) at all three instrument locations. The red lines within the blue areas are low-pass filtered versions of the blue lines (only signals with periods longer than about a minute are shown). Therefore, the relatively high frequency ground shaking and microseismic noise generated by ocean swells do not show up on the redline, but tsunami waves with a period of 10-20 minutes, if present, should be indicated by the red line. A tsunami was not detected by Ocean Networks Canada scientists who examined these data.

The tsunami generated by this earthquake was not nearly as large and devastating as those that struck Sri Lanka, Indonesia and Japan in recent years, because it likely 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.

Ocean Networks Canada - alaska

Resilience through preparedness: remembering the 1964 ‘Good Friday’ tsunami

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Data from Alaska’s Magnitude 7.9 Earthquake and Tsunami

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Negligible Tsunami From Alaska Earthquake

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