Ocean Networks Canada - seismic

ONC’s new dashboard tracks earthquakes around the world

vkeast@uvic.ca — Wed, 21 Oct 2015 20:43:47 +0000

A magnitude 7.1 earthquake occurred at 21:52:02 (UTC) on October 20, 2015, near the Vanuatu Islands in the south Pacific’s volcanically active region located on the Ring of Fire.

Ocean Networks Canada (ONC) is delighted to announce a new interactive dashboard that lets you explore recent earthquakes occurring anywhere in the world, like this one, and those right on our doorstep on the west coast of Canada.

Seafloor seismometers that are connected to the ONC observatory in the northeast Pacific detect signals from most major earthquakes, no matter where they originate on the planet.

The dashboard enables you to explore a selection of recent earthquakes based on time, epicentre location and magnitude.

For each earthquake you can see its distance from the ONC seismometers and inspect the seismometer signals indicating the arrival of the earthquake's ground-shaking seismic waves.

Stop by and explore! (click on the map)

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.

Seismic Shift in Whale Studies

rlat@uvic.ca — Tue, 21 Feb 2012 08:00:00 +0000

Fin whales are the world’s 2nd largest whale species (blue whales are the largest). These majestic creatures inhabit temperate to sub-arctic waters in both the northern and southern hemispheres. Within the Pacific Ocean basin, there are at least 3 geographically distinct populations.

In the North Pacific Ocean, fin whales have been observed as far north as the Chukchi Sea during the summer months while in winter, they spend their time off the coasts of Korea and Japan in the West Pacific, and off northern Baja California in the East Pacific.

The movements and distributions of fin whales in the North Pacific and other oceans remain poorly understood. Several methods have been used to determine the movements of fin whales, including visual and aerial surveys, genetic studies, and the compilation of historic whaling records. Passive acoustic monitoring, via instruments like hydrophones for example, has also been an effective way to study fin whales, whose loud, highly consistent calls are relatively easy to identify.

Other long-term, fixed ocean sensors are becoming increasingly important resources for scientists studying marine animals in their environments. These new approaches include a novel use of seismometer data by researchers at the University of Washington in Seattle. Michelle Weirathmueller and Dax Soule are students in William Wilcock’s research group at the University of Washington’s School of Oceanography, who have been studying the low-frequency calls of fin and blue whales in seismic data. They’ve been delving into seismic data from the Keck Seismic Network and NEPTUNE Canada’s regional network, both situated in the Northeast Pacific Ocean off the coast of Vancouver Island.

Recording of fin whale calls extracted from seismic data and sped up 15x.

Between 2003 and 2006, eight ocean bottom seismometers were deployed in the Keck Network near the Endeavour segment of the Juan de Fuca Ridge. The goal of the experiment was to investigate the relationship between seismic activity and hydrothermal venting. When the collected data were analyzed, it became apparent that earthquakes were not the only signals to have been recorded by the instruments: fin and blue whale calls were also recorded throughout much of the dataset. By studying these data, Michelle and Dax were able to count, locate and track vocalizing fin whales as they swam near the network.

More than 300,000 calls were detected over the three-year Keck Network deployment at Endeavour, with most of the calls occurring during the fall and winter. This pattern of winter detection is shown in the following three histograms. The 2004-2005 data reveals a much lower call count, possibly indicating a response to variations in surface temperature and other environmental conditions, but it is difficult to confirm patterns and hypothesize causes from only three years of data.

Since the Keck Network consisted of eight instruments placed nearby each other, it was possible to locate and track calling fin whales as they swam past the various seismometers. From the first year of data, more than 150 whale tracks were resolved, revealing distinct groupings of call patterns and swimming direction throughout the year. The following graph shows that during the late summer and fall months, the recorded whales tended to swim in a northward direction; there was more of a balance between northward and southward movements in the winter months.

In the analyses of Keck Network seismic data, detections of whale calls were limited to fin and blue whales, whose call frequencies are similar to the seismic waves produced by earthquakes and recorded by the seismometers in place on the seafloor. A subsea cabled observatory also provides significant increased data capacity allowing for the collection of hydrophone data that broaden the range of frequencies scientists can record and study. Some preliminary results from the NEPTUNE Canada hydrophone data are shown below.

As the Keck Network dataset continues to be analyzed, interesting patterns are emerging; a longer time series, however, would allow scientists to more accurately match whale call patterns with seasonal and year-to-year changes in the environment. Ocean-bottom seismometers are being reinstalled at Endeavour as part of the NEPTUNE Canada regional network, which will allow for continuation of this study. Increased data from more NEPTUNE Canada locations and other long-term observation sites will also allow researchers to compare distributions over a larger area. These studies will help scientists like Michelle and Dax to better understand the still-elusive movements and distributions of fin whales and other marine mammals.

Thanks to Michelle Weirathmueller and Dax Soule for their many contributions to this story.

New Boreholes Prepared

rlat@uvic.ca — Tue, 16 Nov 2010 08:00:00 +0000

The JOIDES Resolution research drillship, a key vessel in the Integrated Ocean Drilling Program (IODP), was docked in Victoria this summer for three months of refit work before heading out on two cruises in July and September.

New Boreholes

The Juan de Fuca Plate is a hot-spot of scientific ocean drilling. Since ODP expedition 139 in 1991, numerous boreholes have been drilled in the Northeast Pacifc and several of them where equipped with CORK (Circulation Obviation Retrofit Kit) hydrologic observatories. These CORKs enable geoscientists to observe changes in subsurface pressures and temperatures caused by earthquakes, storms, hydrothermal convection and regional plate strain. NEPTUNE Observatory is collaborating with IODP to provide live connections to CORKs in deep-sea boreholes at NC node locations Cascadia Basin, Clayoquot Slope and our planned future node at Middle Valley.

During the Juan de Fuca Hydrogeology Expedition 327 (July 5–September 5) in the mid-plate area near our Cascadia Basin node location, two new CORKs were installed in boreholes drilled about 360, and 530 meters deep into the ocean floor. In addition to scientific instruments that measure pressures and temperatures, these CORKs are equipped with fluid samplers that collect pore water samples from the sediment covered oceanic crust. These samples will be recovered in the future and analyzed by geochemists and marine microbiologists. In September 2009, the CORK installed in ODP borehole 1026B was connected to NEPTUNE. It is the first CORK observatory with real-time access to its temperature and pressure data. The 1027 area near the centre of the Juan de Fuca Plate is important for several of Ocean Networks Canada’s research projects, including Ocean Crustal Hydrogeology, Seismograph Networkand the West Coast “Tsunami-meter”.

Advanced CORK Installation

After a 3-day port call with celebrations, ship tours and a short lecture series, the JOIDES Resolution embarked on expedition 328 (Cascadia ACORK; September 9-19) led by Earl Davis (Pacific Geoscience Center) to install a new Advanced CORK observatory (ACORK 1364) in the Cascadia subduction zone, 75 km off the coast of Vancouver Island. This ACORK will help scientists monitor changes in pressure associated with this seismically active setting, and better understand how gas hydrates form. Earl Davis is the Principal Investigator for the Ocean Crustal Hydrogeologyresearch project. Also joining the expedition was Martin Heesemann, Ocean Networks Canada staff scientist for Plate Tectonics and Earthquake Dynamics. In 2011, the new ACORK will be connected to our network, which will provide power and real-time data collection over the coming decades.

ACORK 1364, which extends 300 m into the seafloor, is equipped with five pressure gauges, which monitor fluid pressures at the seafloor and in the sediments 155, 205, 245 and 295 meters below the seafloor. The pressure gauges, located on the CORK head above the seafloor, are connected by hydraulic tubes to external screened sections. These screens allow pressure fluctuations within the pore fluid of the sediments to be transmitted to the pressure gauges, while keeping the mud out. If a seismic event causes compression of the sediments beneath the seafloor, the fluid pressure rises in the sediment pore spaces surrounding the CORK. This pressure increase is felt not only in the surrounding sediment, but also passes through the screens and into the hydraulic tubes. These changes are then measured by pressure sensors attached to the top of each tube in the instrument bay section of the ACORK head.

The ACORK casing itself is empty down to a seal at the bottom. This will allow it to be instrumented with a variety of devices in the future, depending on the needs and interests of scientists trying to understand tectonic processes and crustal hydrogeology in this area.

Ocean Networks Canada - seismic

ONC’s new dashboard tracks earthquakes around the world

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Tsunami alert follows 8.2 quake off Chile

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Seismic Shift in Whale Studies

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New Boreholes Prepared

New Boreholes

Advanced CORK Installation

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