The 2007–2008 Nazko earthquakes were a series of small

volcanic earthquakes A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. On Earth, volcanoes are most often found where tectonic plates are ...

measuring less than 4.0 on the

Richter magnitude scale The Richter scale —also called the Richter magnitude scale, Richter's magnitude scale, and the Gutenberg–Richter scale—is a measure of the strength of earthquakes, developed by Charles Francis Richter and presented in his landmark 1935 ...

. They took place in the sparsely populated

Nazko Nazko is a small ranching and logging community, including a historic First Nations community located 100 km west of Quesnel on the Nazko River in the Central Interior of British Columbia, Canada. Nazko means, "river flowing from the south". ...

area of the Central Interior of

British Columbia British Columbia (commonly abbreviated as BC) is the westernmost province of Canada, situated between the Pacific Ocean and the Rocky Mountains. It has a diverse geography, with rugged landscapes that include rocky coastlines, sandy beaches, ...

Canada Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tot ...

starting on October 9, 2007 and ending on June 12, 2008. They occurred just west of

Nazko Cone Nazko Cone is a small potentially active basaltic cinder cone in central British Columbia, Canada, located 75 km west of Quesnel and 150 kilometers southwest of Prince George. It is considered the easternmost volcano in the Anahim Volcanic ...

, a small tree-covered

cinder cone A cinder cone (or scoria cone) is a steep conical hill of loose pyroclastic fragments, such as volcanic clinkers, volcanic ash, or scoria that has been built around a volcanic vent. The pyroclastic fragments are formed by explosive eruptions o ...

that last erupted about 7,200 years ago. No damage or casualties resulted from the Nazko earthquakes, which were too small to be felt by people, but local

seismograph A seismometer is an instrument that responds to ground noises and shaking such as caused by earthquakes, volcanic eruptions, and explosions. They are usually combined with a timing device and a recording device to form a seismograph. The output ...

s recorded them. The

earthquake swarm In seismology, an earthquake swarm is a sequence of seismic events occurring in a local area within a relatively short period. The time span used to define a swarm varies, but may be days, months, or years. Such an energy release is different f ...

occurred at the eastern end of a known volcanic zone called the

Anahim Volcanic Belt The Anahim Volcanic Belt (AVB) is a west–east trending chain of volcanoes and related magmatic features in British Columbia, Canada. It extends from Athlone Island on the Central Coast, running eastward through the strongly uplifted and deeply ...

. This is an east-west trending line of volcanic formations extending from the Central Coast to the Central Interior of British Columbia.

Geology

The 2007–2008 Nazko earthquake swarm is interpreted to have originated below the surface. The character of the

seismic wave A seismic wave is a wave of acoustic energy that travels through the Earth. It can result from an earthquake, volcanic eruption, magma movement, a large landslide, and a large man-made explosion that produces low-frequency acoustic energy. S ...

s indicated that the swarm originated from a magmatic source. It could have formed as a result of rock fracturing at the tip of a

dike Dyke (UK) or dike (US) may refer to: General uses * Dyke (slang), a slang word meaning "lesbian" * Dike (geology), a subvertical sheet-like intrusion of magma or sediment * Dike (mythology), ''Dikē'', the Greek goddess of moral justice * Dikes, ...

and/or by movement along fault planes due to changes in the local

stress field A stress field is the distribution of internal forces in a body that balance a given set of external forces. Stress fields are widely used in fluid dynamics and materials science. Consider that one can picture the stress fields as the stress cre ...

by the expansion and movement of

magma Magma () is the molten or semi-molten natural material from which all igneous rocks are formed. Magma is found beneath the surface of the Earth, and evidence of magmatism has also been discovered on other terrestrial planets and some natural sa ...

. This magmatic activity is potentially linked to the hypothesized

Anahim hotspot The Anahim hotspot is a hypothesized hotspot in the Central Interior of British Columbia, Canada. It has been proposed as the candidate source for volcanism in the Anahim Volcanic Belt, a long chain of volcanoes and other magmatic features tha ...

, a

mantle plume A mantle plume is a proposed mechanism of convection within the Earth's mantle, hypothesized to explain anomalous volcanism. Because the plume head partially melts on reaching shallow depths, a plume is often invoked as the cause of volcanic hot ...

that is probably responsible for older

volcanism Volcanism, vulcanism or volcanicity is the phenomenon of eruption of molten rock (magma) onto the surface of the Earth or a solid-surface planet or moon, where lava, pyroclastics, and volcanic gases erupt through a break in the surface called ...

throughout the Anahim Volcanic Belt. This

volcanic belt A volcanic belt is a large volcanically active region. Other terms are used for smaller areas of activity, such as volcanic fields. Volcanic belts are found above zones of unusually high temperature () where magma is created by partial melting ...

includes the

Rainbow A rainbow is a meteorological phenomenon that is caused by reflection, refraction and dispersion of light in water droplets resulting in a spectrum of light appearing in the sky. It takes the form of a multicoloured circular arc. Rainbows c ...

, Ilgachuz and Itcha range

shield volcano A shield volcano is a type of volcano named for its low profile, resembling a warrior's shield lying on the ground. It is formed by the eruption of highly fluid (low viscosity) lava, which travels farther and forms thinner flows than the more v ...

es west of the Nazko swarm. Individual Anahim volcanoes generally become older to the west of the Nazko swarm, indicating that the

North American Plate The North American Plate is a tectonic plate covering most of North America, Cuba, the Bahamas, extreme northeastern Asia, and parts of Iceland and the Azores. With an area of , it is the Earth's second largest tectonic plate, behind the Pacific ...

is moving in a westerly direction with respect to the hotspot, carrying the volcanoes along with it at a rate of to per year. Because the area where the 2007–2008 Nazko earthquake swarm originated is at the eastern end of the volcanic belt, it probably represents the youngest portion of the hotspot track. This suggests any future volcanic earthquakes will occur in the Nazko region or further to the east. Anahim Volcanic Belt-en

Before the Nazko earthquake swarm began in 2007, the Anahim hotspot was not known to be an earthquake zone. On October 10 of the following year, a swarm of earthquakes occurred. These earthquakes were normally no more than

magnitude Magnitude may refer to: Mathematics *Euclidean vector, a quantity defined by both its magnitude and its direction *Magnitude (mathematics), the relative size of an object *Norm (mathematics), a term for the size or length of a vector *Order of ...

1.0 on the Richter magnitude scale, but at least one earthquake was as strong as magnitude 3.9. Since the appearance of the Nazko swarm,

Natural Resources Canada Natural Resources Canada (NRCan; french: Ressources naturelles Canada; french: RNCan, label=none)Natural Resources Canada is the applied title under the Federal Identity Program; the legal title is Department of Natural Resources (). is the depa ...

has expressed interest in the adjacent 7,200‑year‑old Nazko Cone. Even though earthquake swarms can be dangerous, scientists are able to model such events to analyze their structure. During the earthquake swarm in 2007, a group of scientists investigated the possibility that a volcanic eruption would occur. Five additional seismographs were placed in the earthquake zone, and scientists closely monitored the seismic activity. After additional data were gathered, scientists with the

United States Geological Survey The United States Geological Survey (USGS), formerly simply known as the Geological Survey, is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, ...

, the

University of Washington The University of Washington (UW, simply Washington, or informally U-Dub) is a public research university in Seattle, Washington. Founded in 1861, Washington is one of the oldest universities on the West Coast; it was established in Seattle a ...

, and other organizations, agreed that the Nazko earthquakes probably originated from movement of magma beneath the surface near Nazko Cone. However, because of the number and small size of the Nazko earthquakes, no volcanic eruption is likely. Other recent earthquakes in North America that have been attributed to magma but did not result in a volcanic eruption include the 2003 earthquakes under

Lake Tahoe Lake Tahoe (; was, Dáʔaw, meaning "the lake") is a Fresh water, freshwater lake in the Sierra Nevada (U.S.), Sierra Nevada of the United States. Lying at , it straddles the state line between California and Nevada, west of Carson City, Nevad ...

in the

U.S. state In the United States, a state is a constituent political entity, of which there are 50. Bound together in a political union, each state holds governmental jurisdiction over a separate and defined geographic territory where it shares its sover ...

California California is a U.S. state, state in the Western United States, located along the West Coast of the United States, Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the List of states and territori ...

and a 2004 earthquake swarm at

Jordan Craters The flows of Jordan Craters volcanic field are the youngest of a series of large Quaternary basalt fields in the eastern part of the U.S. state of Oregon. The field is thought to be approximately 3200 years old, based on findings of a lake sedim ...

in the U.S. state of

Oregon Oregon () is a U.S. state, state in the Pacific Northwest region of the Western United States. The Columbia River delineates much of Oregon's northern boundary with Washington (state), Washington, while the Snake River delineates much of it ...

Number of earthquakes

More than 1,000 earthquakes were recorded by regional seismic networks within three weeks of October 20, 2007. Because the seismometers that recorded the Nazko swarm were more than away from where the earthquakes took place, the locations of the

hypocenter In seismology, a hypocenter or hypocentre () is the point of origin of an earthquake or a subsurface nuclear explosion. A synonym is the focus of an earthquake. Earthquakes An earthquake's hypocenter is the position where the strain energy s ...

s were measured with poor resolution. Following the earthquake, five seismometers were placed by the

Geological Survey of Canada The Geological Survey of Canada (GSC; french: Commission géologique du Canada (CGC)) is a Canadian federal government agency responsible for performing geological surveys of the country, developing Canada's natural resources and protecting the en ...

from September 2007 to June 2008 close to the hypocenter. Analysis of the data recorded by these seismometers indicates a much larger total number of earthquakes. For example, at least 597 earthquakes were recognized during a period of only six hours. At least two episodes of earthquakes constitute the Nazko swarm. In the first seismic phase from October 9 to November 1, 2007, a total of 153 earthquakes took place. During the second seismic phase between September 25, 2007 and June 12, 2008, 4,428 earthquakes occurred. These two seismic episodes were cross-correlated by scientists to understand changes in the development of the earthquake swarm. Correlation coefficients were around 1.0 for the beginnings of the periods of activity, indicating almost identical situations, and then decayed to around 0.5, indicating a decrease in similarity between the later stages of the two events.

Scientific response

The earthquake swarm was noted on October 12, 2007 in the

Prince George Citizen The ''Prince George Citizen'' is a weekly newspaper located in Prince George, British Columbia, Canada. It is owned by Glacier Media. In addition to Prince George, the ''Citizen'' also covers the outlying communities of Fort St. James, Fraser ...

by citizen staff, three days after the earthquakes began. Scientists mentioned in the report were seismologist John Cassidy of Natural Resources Canada and volcanologist Catherine Hickson, who was part of the Geological Survey of Canada at the time. At the time of the report, scientists did not know the origin of the swarm. Seismologist John Cassidy stated, "the depth is enough to rule out hydrothermal but it's up in the air as to whether the cause is tectonic shifts or volcanic activity. If it is volcanic there are certain characteristics that we would expect, there's a tremor-like character to it. And so we'll be looking for the types of events that we see beneath volcanoes and we'll be looking to see if they're getting closer to the surface or if they're migrating at all." Even if the Nazko swarm were a warning of a volcanic eruption, Hickson doubted it would turn out to be a highly

explosive eruption In volcanology, an explosive eruption is a volcanic eruption of the most violent type. A notable example is the 1980 eruption of Mount St. Helens. Such eruptions result when sufficient gas has dissolved under pressure within a viscous magma such ...

like those that can occur in subduction-zone volcanoes. "We're not talking about an injection of tonnes of ash many kilometers into the air like the 1980 Mount St. Helens eruption or the 1991

Mount Pinatubo Mount Pinatubo is an active stratovolcano in the Zambales Mountains, located on the tripoint boundary of the Philippine provinces of Zambales, Tarlac and Pampanga, all in Central Luzon on the northern island of Luzon. Its eruptive history w ...

eruption. We're talking about something very small, relatively localized that should have a fairly limited impact... but it'll be extremely exciting", Hickson said. If an eruption were to occur, Hickson suggested that it would be characterized by a

lava fountain Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a moon onto its surface. Lava may be erupted at a volcano or through a fracture in the crust, on land or und ...

that sends globs of lava into the air. This is similar to those that occur in Hawaii. Hickson said that a Nazko eruption could be a tourist attraction, but warned that noxious gases such as

carbon dioxide Carbon dioxide (chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is transpar ...

and

sulfur dioxide Sulfur dioxide (IUPAC-recommended spelling) or sulphur dioxide (traditional Commonwealth English) is the chemical compound with the formula . It is a toxic gas responsible for the odor of burnt matches. It is released naturally by volcanic activ ...

would be released during the event.

Preparedness and hazards

Because no seismographs were close enough to the Nazko swarm zone before the earthquakes began, employees of

placed seismographs in the area to monitor future earthquakes in the area more clearly. An infrasound station is also being established, which is able to measure

sound wave In physics, sound is a vibration that propagates as an acoustic wave, through a transmission medium such as a gas, liquid or solid. In human physiology and psychology, sound is the ''reception'' of such waves and their ''perception'' by the ...

s that would normally go unnoticed by human hearing. These stations can detect volcanic eruptions and the release of gas at volcanic vents, and can be used in combination with other geophysical data to monitor fluid flow within volcanoes. Employees of Natural Resources Canada have also visited two communities that were adjacent to the 2007–2008 earthquake swarm to renew information about the Nazko swarm, collect samples, and examine some of the more poorly studied volcanic deposits in the Nazko region. The Natural Resources Canada employees also measured carbon dioxide levels during the earthquake swarm. Carbon dioxide is usually discharged at faults in volcanically active areas and can collect in

soil Soil, also commonly referred to as earth or dirt, is a mixture of organic matter, minerals, gases, liquids, and organisms that together support life. Some scientific definitions distinguish ''dirt'' from ''soil'' by restricting the former te ...

and under snow. Because of this, carbon dioxide concentrations can provide information on volcanic activity in the subsurface. The Nazko swarm did not cause any discernible discharge of carbon dioxide, which is normal for non-eruptive events. Nazko Cone, British Columbia

The 2007–2008 Nazko earthquake swarm is one of numerous seismic events that have occurred near volcanoes in British Columbia. Volcanoes that have experienced volcanic earthquakes include the

Mount Meager massif The Mount Meager massif is a group of volcanic peaks in the of the Coast Mountains in southwestern British Columbia, Canada. Part of the Cascade Volcanic Arc of western North America, it is located north of Vancouver at the northern end of the ...

(seventeen events),

Mount Cayley Mount Cayley is an eroded but potentially active stratovolcano in the Pacific Ranges of southwestern British Columbia, Canada. Located north of Squamish, British Columbia, Squamish and west of Whistler, British Columbia, Whistler, the volcano ...

(four events),

Mount Garibaldi Mount Garibaldi (known as Nch'kaý to the indigenous Squamish people) is a dormant stratovolcano in the Garibaldi Ranges of the Pacific Ranges in southwestern British Columbia, Canada. It has a maximum elevation of and rises above the surroundi ...

(three events),

Silverthrone Caldera The Silverthrone Caldera is a potentially active caldera complex in southwestern British Columbia, Canada, located over northwest of the city of Vancouver and about west of Mount Waddington in the Pacific Ranges of the Coast Mountains. The cald ...

(two events), Castle Rock (two events),

Hoodoo Mountain Hoodoo Mountain, sometimes referred to as Hoodoo Volcano, is a potentially active stratovolcano in the Northern Interior of British Columbia, Canada. It is located northeast of the Alaska–British Columbia border on the north side of the Isk ...

(eight events), Crow Lagoon (four events), The Volcano (five events), and the

Mount Edziza volcanic complex The Mount Edziza volcanic complex is a large and potentially active north-south trending complex volcano in Stikine Country, northwestern British Columbia, Canada, located southeast of the small community of Telegraph Creek. It occupies the sout ...

(eight events). Seismic data suggest that these volcanoes still contain active

magma chamber A magma chamber is a large pool of liquid rock beneath the surface of the Earth. The molten rock, or magma, in such a chamber is less dense than the surrounding country rock, which produces buoyant forces on the magma that tend to drive it upw ...

s, indicating possible future eruptive activity. Although the available data do not allow a clear conclusion, these observations are indications that some of Canada's volcanoes may be active, with significant potential dangers. This seismic activity correlates both with some of Canada's most youthful volcanoes and with long-lived volcanoes with a history of significant explosive activity, such as Hoodoo Mountain and the Mount Edziza volcanic complex. If magma were to rise towards the surface of Nazko, new earthquake swarms would occur, with a significant increase in the size and number of earthquakes. An eruption in the Nazko area would probably create a small cinder cone, similar to what formed Nazko Cone 7,200 years ago. Immediate hazards related to cinder cone eruptions in the Nazko area would probably be forest fires and, if an

eruption column An eruption column or eruption plume is a cloud of super-heated ash and tephra suspended in gases emitted during an explosive volcanic eruption. The volcanic materials form a vertical column or plume that may rise many kilometers into the air a ...

were produced, redirection of nearby air traffic.

References

{{DEFAULTSORT:Nazko earthquakes, 2007-2008 2007 earthquakes 2007 in British Columbia 2007 in science 2008 earthquakes 2008 in British Columbia 2008 in science 21st-century volcanic events Anahim Volcanic Belt Central Interior of British Columbia Earthquakes in British Columbia Holocene volcanism Hotspot volcanism Earthquake swarms Volcanic earthquakes

Geology

Number of earthquakes

Scientific response

Preparedness and hazards

See also

References