Ocean Networks Canada - megathrust earthquake

Are earthquakes on the rise?

kshoemak@uvic.ca — Wed, 25 Jan 2017 20:45:05 +0000

With media coverage of the recent earthquakes in Italy (M6.6), New Zealand (M7.8), Japan (M6.9), and Papua New Guinea (M7.9), you might be wondering whether earthquake activity is increasing. Long-term earthquake statistics in the last 12 months indicate that it was an average year: there were no earthquakes of M8.0 or higher (one M8.0+ is the annual average) and 19 earthquakes with M7.0 - 7.9 (17 is the annual average). These statistics (Figure 1) show that earthquake activity is not increasing.

Figure 1: Annual global earthquakes by magnitude, based on USGS statistics.

When the media focusses attention on something, such as the recent earthquakes in Italy, it’s easy to believe that there’s simply more of it about. This is called a spotlight fallacy, which contributes to the impression that earthquakes are on the rise. In fact, there have been almost 40 quakes of M6.6 or greater in the last year, but most of them did not create as much damage, nor did they receive as much attention.

Similarly, we are also susceptible to the clustering illusion. Our logical brains are wired to seek meaning in clusters or “streaks”, even if the occurrence is totally random. When in doubt, turn to scientific facts—especially during the post-truth era.

Earthquake Facts

A measureable earthquake takes place every 3-4 minutes somewhere on Earth.
Approximately 500,000 earthquakes are detected every year. This animation shows every recorded earthquake in sequence as they occurred from 1 January 2001 to 31 December 2015.
Magnitude and Intensity measure different characteristics of earthquakes. Magnitude indicates the energy released at the source of the earthquake and is measured by seismographs. Intensity indicates the strength of shaking produced by the earthquake at a certain location and is determined from the effects on people, human structures, and the natural environment (USGS).
Recent earthquakes around the world can be explored using the Ocean Networks Canada’s (ONC) interactive earthquake data dashboard (Figure 2). The dashboard includes selected earthquakes that are likely to have been recorded on ONC sensors.

Figure 2: ONC earthquake data dashboard.

The largest earthquake recorded by modern instruments happened in Chile on 22 May 1960 (M9.5).
The deadliest earthquake on record struck Shansi, China on 23 January 1556. An estimated 830,000 people died.
The Pacific northwest is host to three kinds of tectonic earthquakes: M9.0 Cascadia megathrust quakes, M6.5 to 7 deep earthquakes, and shallow crustal-fault earthquakes up to M7.5.
A megathrust earthquake is caused by a sudden slip on the fault between two tectonic plates (Figure 3) when one is forced under the other. On Canada’s west coast for example, the Juan de Fuca plate (Figure 4) is moving eastward underneath the North America plate at a rate of a few centimetres per year.

Figure 3: Global tectonic plates were mapped in the second half of the 20th century. (Image credit: Wikipedia)

Megathrust earthquakes tend to occur in the Pacific northwest region approximately every 300-500 years.
The last megathrust subduction earthquake to occur along the Cascadia subduction zone happened on 26 January 1700. The magnitude was estimated as 9.0, resulting in a tsunami that was recorded in Japan. Evidence of this earthquake is confirmed by geological evidence (land level changes, tsunami traces, turbidite deposits), biological evidence (tree rings), and human records (Indigenous stories and Japanese records). Find out more.

Figure 4: The Cascadia Subduction Zone, where the Juan de Fuca plate is forced under the continental North America Plate. (Image credit: USGS).

In collaboration with the Government of British Columbia, ONC is developing an earthquake early warning system (Figure 5) to alert British Columbians in advance of an earthquake. There are currently no known means to reliably predict earthquakes, however seismic instruments can rapidly detect an earthquake as it begins to unfold and communicate a warning up to 90 seconds before shaking arrives.

Figure 5: Earthquakes release energy that travels through the Earth as seismic waves. Primary or ‘P’ waves travel faster than secondary or ‘S’ waves that cause damaging ground shaking. It is the ability to detect these first ‘P-waves’ that enables earthquake early warning systems to deliver alerts before the arrival of the ‘S-waves’.

Find out more about British Columbia’s earthquake early warning system which will be installed, tested and delivered to Emergency Management BC by March 2019.

Making progress on earthquake early warning

vkeast@uvic.ca — Sat, 30 Jan 2016 01:13:37 +0000

During the night on 27 January 1700, a powerful magnitude 9 earthquake ruptured the Pacific coast along the Cascadia subduction fault zone. Historical records, as far away as Japan, confirm this devastating event.

Fast forward 316 years. Scientists now believe that major fault lines build up pressure over hundreds of years, and eventually release the pressure as a megathrust earthquake. Before that can happen, Ocean Networks Canada is poised to send an advance warning with sensors and software that can detect an earthquake—up to 90 seconds before the major shaking starts.

Earthquake early warning is a vital part of preparing for, and responding to, a major earthquake. It’s about delivering critical seconds of action that will save lives, reduce damage, support emergency response and kick-start recovery operations.

While Pacific nations such as Japan and Taiwan have fully integrated earthquake early warning systems, western North America is still in the building stages. An effective system requires collaboration among leaders and innovators in science, engineering and public safety—organizations such as Natural Resources Canada, British Columbia’s Ministry of Transportation and Infrastructure, Emergency Management BC, the University of British Columbia, the University of Victoria’s Ocean Networks Canada and many others.

This concentration of planning is mirrored south of the border where people and government agencies are equally wary of the locked plates of the Cascadia subduction zone, stretching from northern California to British Columbia.

A key piece in the puzzle: offshore sensors

Ocean Networks Canada operates observatory sites on the Cascadia subduction zone, with a number of seismic sensors sitting on the Juan de Fuca plate, on or close to the major fault line. This proximity allows for faster alerts that can provide coastal communities and urban centres with precious seconds to take action, before the major shaking starts.

More sensors, both on the seafloor and on land, would increase the areas monitored and provide a denser, more effective network, in line with the proven system that blankets Japan.

Earthquake detection: It’s time to finish the network (CBC.ca/ 27 Oct 2015 )

Directing disaster info into the right hands with WARN

ONC’s Web-enabled Awareness Research Network (WARN) software platform currently being tested, will deliver notification of impending earthquake shaking —almost immediately—that let emergency decision-makers and automatic safeguard systems take critical actions such as shutting down gas lines, pausing elevators, keeping firehall doors raised, halting surgery, stopping bridge traffic and slowing down trains.

Coordinating data from a number of sensors in different locations, WARN does not just detect events; it also makes measurements such as the severity and epicentre of an earthquake, or the speed and direction of a tsunami.

WARN: providing rapid notifications to alert communities (Canada's Advanced Research and Innovation Network brochure)

Looking to the near future: collaborations are key

British Columbia will be testing its first full scale mock earthquake scenario and immediate response plan in June at Port Alberni, on Vancouver Island. ‘Exercise Coastal Response’ is a million-dollar exercise that will include all levels of government, Indigenous peoples, first responders and other specialists.

ONC also plans to install additional earthquake early warning sensors on land and offshore, during this summer’s Wiring the Abyss expedition.

“Effective earthquake early warning really is a shared responsibility. We’re all in this together: scientists, engineers and elected officials, plus every family and individual in British Columbia. We have the people and the expertise and the will. Let’s be ready for the big one.” Kate Moran, ONC President & CEO

Related stories:

Researchers look to improve earthquake warning system (Victoria Times Colonist, October 2016)

PDF File:

WARN Fact Sheet 2015