Category:Earthquakes in British Columbia
Pages in category "Earthquakes in British Columbia"
The following 8 pages are in this category, out of 8 total. This list may not reflect recent changes (learn more).
The following 8 pages are in this category, out of 8 total. This list may not reflect recent changes (learn more).
1. 1700 Cascadia earthquake – The 1700 Cascadia earthquake occurred along the Cascadia subduction zone on January 26 with an estimated moment magnitude of 8. 7–9.2. The length of the rupture was about 1,000 kilometers with an average slip of 20 meters. The earthquake caused a tsunami struck the coast of Japan, and may also be linked to the Bonneville Slide. It is suggested that the 1700 earthquake took place at about 21,00 on January 26,1700, the Japanese records exist primarily in the prefecture of Iwate, in communities such as Tsugaruishi, Kuwagasaki and Ōtsuchi. This includes both inland stands of trees, such as one on the Copalis River in Washington, and pockets of tree stumps that are now under the ocean surface, sediment layers in these locations demonstrate a pattern consistent with seismic and tsunami events occurring around this time. Core samples from the floor, as well as debris samples from some earthquake-induced landslides in the Pacific Northwest. Archaeological research in the region has uncovered evidence of coastal villages having been flooded and abandoned around 1700. Local Native American and First Nations groups residing in Cascadia did not have a tradition of record-keeping. However, numerous oral traditions describing a great earthquake and tsunami-like flooding exist among indigenous peoples from British Columbia to Northern California. Masit was the community on Pachina Bay not to have been wiped out. Makah stories from Washington speak of a great earthquake, of which the only survivors were those who fled inland before the tsunami hit. The Quileute people in Washington have a story about a flood so powerful that villagers in their canoes were swept all the way to the Hood Canal. The geological record reveals that great earthquakes occur in the Cascadia subduction zone about every 500 years on average, there is evidence of at least 13 events at intervals from about 300 to 900 years with an average of 570–590 years. Previous earthquakes are estimated to have occurred in 1310 AD,810 AD,400 AD,170 BC and 600 BC. These cities do have many structures, especially bridges and unreinforced brick buildings, consequently. Recent findings conclude that the Cascadia subduction zone is more complex, geologists have also determined the Pacific Northwest is not prepared for such a colossal quake. The tsunami produced could reach heights of 80 to 100 feet, a 2004 study revealed the potential for relative mean sea level rise along the Cascadia subduction zone. It postulated that cities on the west coast of Vancouver Island, such as Tofino and Ucluelet, are at risk for a 1–2 m subsidence, some other subduction zones have such earthquakes every 100 to 200 years, the longer interval results from slower plate motions
2. 1946 Vancouver Island earthquake – The 1946 Vancouver Island earthquake occurred with a moment magnitude of 7.3 that struck Vancouver Island, on the Coast of British Columbia, Canada, at 10,15 a. m. on June 23. The main shock occurred in the Forbidden Plateau area northwest of Courtenay. While most of the earthquakes in the Vancouver area occur at tectonic plate boundaries. Shaking was felt from Portland, Oregon to Prince Rupert, British Columbia and this earthquake is Canadas largest historic onshore earthquake.1 on the moment magnitude scale. The tectonics that caused the 1946 Vancouver Island earthquake are poorly known, no surface expression of the offset was noticed, most likely because the epicentre area is very remote and densely forested. The estimated depth of the places it within the continental crust, not at the margin with the Cascadia subduction zone. Specifically, the epicentre was positioned somewhere in the Forbidden Plateau region. Though very destructive, the earthquake caused two deaths, Jacob L. Kingston, aged 69, and Daniel Fidler, who was 50. Kingston suffered an attack, while Fidler drowned when his dinghy was swamped by a wave. In Vancouver, damage consisted of lofty buildings oscillating violently, in addition, within the city, at least one gas line cracked and several power outages occurred. Fires broke out in several chimneys, and at least one bridge was fractured by the shaking. In the Hotel Vancouver, which housed the elderly and caught on fire, more than 500 war veterans families fled the flames. One writer, George Finley, stated that the Lions Gate Bridge swayed like a leaf, coinciding with a low, rumbling sound, some chimneys were fractured in Victoria, and people in Victoria and Vancouver experienced great fright, with some seen fleeing into the streets. Landslides created by the earthquake were common throughout Vancouver Island, land subsidence resulted from the earthquake, most commonly around shorelines on the Strait of Georgia. This included the bottom of Deep Bay which sank between 2.7 m and 25.6 m and these measurements were reported by the Canadian Hydrographic Service. Also, a 3-metre ground shift occurred on Read Island, ships throughout the region were affected, and those on board them during the earthquake described it as similar to having run over a sand bar or striking a rock. Undersea power lines were destroyed in the long narrow Alberni Inlet, all lighthouse keepers in the surrounding area felt the earthquake, and experienced damage including shattered windows and smashed dishes. A tsunami struck the west coast of Texada Island with two waves, the first being 2 metres high and the second 1 metre high, the earthquake caused a landslide near Mount Colonel Foster
3. 1964 Alaska earthquake – The 1964 Alaskan earthquake, also known as the Great Alaskan earthquake and Good Friday earthquake, occurred at 5,36 P. M. AST on Good Friday, March 27, across south-central Alaska, ground fissures, collapsing structures, and tsunamis resulting from the earthquake caused about 139 deaths. Lasting four minutes and thirty-eight seconds, the magnitude 9.2 megathrust earthquake was the most powerful recorded in North American history, soil liquefaction, fissures, landslides, and other ground failures caused major structural damage in several communities and much damage to property. Anchorage sustained great destruction or damage to many inadequately earthquake engineered houses, buildings, two hundred miles southwest, some areas near Kodiak were permanently raised by 30 feet. Nearby, a 27-foot tsunami destroyed the village of Chenega, killing 23 of the 68 people who lived there, survivors out-ran the wave, climbing to high ground. Post-quake tsunamis severely affected Whittier, Seward, Kodiak, and other Alaskan communities, as well as people and property in British Columbia, Washington, Oregon, tsunamis also caused damage in Hawaii and Japan. Evidence of motion directly related to the earthquake was reported from Florida. Alaska Standard Time, a fault between the Pacific and North American plates ruptured near College Fjord in Prince William Sound, the epicenter of the earthquake was 12.4 mi north of Prince William Sound,78 miles east of Anchorage and 40 miles west of Valdez. The focus occurred at a depth of approximately 15.5 mi, ocean floor shifts created large tsunamis, which resulted in many of the deaths and much of the property damage. Large rockslides were also caused, resulting in property damage. Vertical displacement of up to 38 feet occurred, affecting an area of 100,000 miles² within Alaska, studies of ground motion have led to a peak ground acceleration estimate of 0. 14–0.18 g. The Alaska earthquake was a subduction zone earthquake, caused by an oceanic plate sinking under a continental plate, the fault responsible was the Aleutian Megathrust, a reverse fault caused by a compressional force. This caused much of the ground which is the result of ground shifted to the opposite elevation. Two types of tsunamis were produced by subduction zone earthquake. There was a tectonic tsunami produced in addition to about 20 smaller and these smaller tsunami were produced by submarine and subaerial landslides and were responsible for the majority of the tsunami damage. Tsunami waves were noted in over 20 countries, including, Peru, New Zealand, Papua New Guinea, Japan, the largest tsunami wave was recorded in Shoup Bay, Alaska, with a height of about 220 ft. The quake was a reported XI on the modified Mercalli Intensity scale indicating major structural damage, property damage was estimated at about $311 million. Most damage occurred in Anchorage,75 mi northwest of the epicenter, the neighborhood lost 75 houses in the landslide, and the destroyed area has since been turned into Earthquake Park
4. 2012 Haida Gwaii earthquake – The 2012 Haida Gwaii earthquake occurred just after 8,04 p. m. PDT on October 27. The shock had a moment magnitude of 7.8 and a maximum Mercalli Intensity of V, the earthquakes epicentre was on Moresby Island of the Haida Gwaii archipelago. This was the second largest Canadian earthquake ever recorded by a seismometer, after the 1949 Queen Charlotte Islands earthquake, strong shaking was felt throughout Haida Gwaii where residents in Masset, Skidegate, Sandspit, and Queen Charlotte City were evacuated to higher ground. Minor shaking was felt in Prince Rupert and in cities of the Interior such as Prince George, Quesnel. Electricity service was interrupted in Bella Coola, the 2012 quake exhibited a thrust mechanism, more characteristic of the Cascadia Subduction Zone to the south. A tsunami warning was issued for the North American Coast from the Alaskan Panhandle to Vancouver Island, Canadian authorities were questioned for issuing a tsunami warning nearly 40 minutes after the U. S. had issued their warning. The greatest wave heights recorded at tide gauges in Canada were 0. 25m at Langara Island and 0. 22m at Winter Harbour, in Tofino on Vancouver Island, the tsunami warning sirens were activated and residents in low-lying areas evacuated their homes. The maximum wave height recorded in Tofino was 0. 09m, tofinos tsunami warning system was activated after communication with the provincial coordinating centre was cut off. In the U. S. Hawaii was also placed on alert, the maximum wave height recorded at tide gauges in Hawaii was 0. 79m. Other warnings were issued for the states of Oregon and California, despite the earthquakes large magnitude, no major structural damage was reported from any of the population centres in the vicinity. This can be explained by the remoteness of the tremors epicentre, no casualties or major injuries were recorded from the quake, likely due to the sparsely populated nature of the region. As a result of the earthquake and its aftershocks, the hot springs in Gwaii Haanas National Park on Hotspring Island dried up. There were 94 aftershocks of magnitude 4.0 or greater lasting until November 7, the largest of these numerous aftershocks was a 6.3 magnitude earthquake that occurred 56 kilometres to the west of the main tremor on the morning of October 28. This was followed on October 29 by a 6.2 aftershock 50 kilometres to the south of the original quake
5. Cascadia subduction zone – The Cascadia subduction zone is a convergent plate boundary that stretches from northern Vancouver Island to northern California. It is a long, sloping subduction zone that separates the Explorer, Juan de Fuca, and Gorda plates, on the one hand. The denser oceanic plate is subducting beneath the less dense continental plate offshore of British Columbia, Washington, Oregon, the North American Plate is moving in a southwest direction, overriding the oceanic plate. The Cascadia subduction zone is where the two plates meet, tectonic processes active in the Cascadia subduction zone region include accretion, subduction, deep earthquakes, and active volcanism of the Cascades. This volcanism has included such notable eruptions as Mount Mazama about 7,500 years ago, Mount Meager about 2,350 years ago, and Mount St. Helens in 1980. Major cities affected by a disturbance in this zone include Vancouver and Victoria, British Columbia, Seattle, Washington. In the 1960s, underground fractures were uncovered by oil companies in Puget Sound and these were believed to be inactive through the 1990s. In the 1980s, geophysicists Tom Heaton and Hiroo Kanamori of Caltech compared the generally quiet Cascadia to more active subduction zones elsewhere in the Ring of Fire, at the time of the 1700 earthquake, there were no written records of the event in Cascadia. Orally-transmitted legends from the Olympic Peninsula area talk of a battle between a thunderbird and a whale. Therefore, in a 2005 study, seismologist Ruth Ludwin set out to collect, reports from the Huu-ay-aht, Makah, Hoh, Quileute, Yurok, and Duwamish peoples referred to earthquakes and saltwater floods. This collection of data allowed her team to come up with a date range for the event. During low tide one day in March 1986, paleogeologist Brian Atwater dug along Neah Bay using a nejiri gama, underneath the top layer of sand, he uncovered a distinct plant—arrowgrass—that had grown in a layer of marsh soil. This was proof that the ground had suddenly sunk under sea level, the events had happened so quickly as to cause the top layer of sand to seal away any air, thus preserving the centuries-old plants. In 1987, Atwater mounted another expedition paddling up the Copalis River with Dr. David Yamaguchi, who was then studying the eruptions of Mount St. Helens. The pair happened upon a section of ghost forest, so-called due to the dead, originally thought to have died slowly due to a gradual rise in sea level, closer inspection yielded a different story, the land plummeted up to two meters during an earthquake. Having initially tested spruce using tree-ring dating, they found that the stumps were too rotted to count all the outer rings. However, upon having examined those of the red cedar and comparing them to the living specimens meters away from the banks. There were rings up until the year 1690, indicating that the incident had occurred shortly thereafter, root samples confirmed their conclusion, narrowing the time frame to the winter of 1699 to 1700