Description Of The Event That Caused The Earthquake

In conclusion the recent conception and development of plate tectonic theory has greatly aided our understanding of the distribution of seismic events. We now understand that there is a correlation between earthquakes/volcanoes locations and their proximity to a plate boundary plates are continually moving and earthquakes and volcanoes are found along these boundaries. Exceptions to this rule such as Hawaii also help prove tectonic theory due to their unique creation. Whilst this has helped our understanding we also recognise the fact those in LEDCs with poor access to education are unaware of plate tectonic theory so they cannot understand the hazards that some countries face, nor have the means to mitigate against them thus worsening the

The earthquake was located on the San Andreas fault which is a seismic zone between two of the earth’s tectonic plates. Seismic events which occur is caused as a result of the earth’s tectonic plates moving against each other and this can cause huge earthquakes and volcanoes (“Young”). The transform boundary passes through California and this is where the Pacific and North American plates move past each other without colliding. The event in which this occurred was the San Andreas fault (“Young”). When the plates move past each other and the resistance builds up, this causes an earthquake like the 1906 San Francisco earthquake. This earthquake caused a separation and displacement in the landscape which was seen over several kilometers

On January 12th, 2010, the small country of Haiti was hit by a 7.0 magnitude earthquake that devastated the city of Port-au-Prince and surrounding areas (Haiti earthquake of 2010, 2015). The 30-second disaster was just the beginning of a collection of aftershocks that then struck the country relentlessly for days (Haiti earthquake of 2010, 2015). Many areas were reduced to rubble leaving approximately one million Haitians homeless and 350 000 dead and another 300 000 injured (Haiti earthquake of 2010, 2015). The ill-prepared country was sitting on two tectonic plates- the Caribbean and the North American, where there was slippage resulting in the earthquake (KS3 Bitesize Geography). Following the environmental catastrophe, the international community responded, and a relief effort began (Haiti earthquake of 2010, 2015).

• This earthquake may not have released all of the strain stored in its rocks next to the fault this reveals a potential earthquake in the Santa Cruz Mountains in the near future. The occurrence of the earthquake showed that the Earth did not exhaust all its strain and hence other earthquakes could be expected. However, the dates could not be predicted. The extent of the damage could have been much more devastating for the region, but with the earthquake occurring near the coast this made half of the felt area westward in the Pacific Ocean. The occurrence of aftershocks ten days later reinforces the unpredictability nature and hence makes Geology to be a study that is always evolving. In conclusion, the Earth and the study of cannot be exhausted as every natural occurrence provides a new puzzle to be solved.

The 1906 San Francisco Earthquake tectonic setting was in the outermost shell of earth known as the crust this is composed of rigid plates that have been moving for hundreds of millions of years. Two of these moving plates meet in western California; the boundary between them is a zone of faults, the principal one being the San Andreas fault. The horizontal sliding of the Pacific Plate relative to the North American Plate, causes earthquakes along the San Andreas fault and similar plates near the region. The San Andreas fault is a transform plate boundary, accommodating horizontal relative motions (usgs.gov).

The tectonic setting for the 1906 San Francisco Earthquake was in the outermost shell of earth consisting of rigid plates that have been moving for hundreds of millions of years. Two of these moving plates meet in western California; the boundary between them is a zone of faults, the principal one being the San Andreas fault. The Pacific Plate (on the west) slides horizontally northwestward relative to the North American Plate (on the east), causing earthquakes along the San Andreas and associated faults. The San Andreas fault is a transform plate boundary, accommodating horizontal relative motions (usgs.gov).

The right figure gives a more specific visualization of the Juan de Fuca plate currently been forced to slip under the North American plate in an area known as the Cascadia Subduction Zone. Along the boundary of these two plates, a section has become locked yet they are still moving toward each other. As a result, stress has accumulated for centuries and when that stress relieved, it will cause the largest and most powerful earthquake called a megathrust earthquake of magnitude 9.0 or higher. The last earthquake which was caused by the relieved of this stress with similar magnitude happened in 1700. The scientists were able to determine this date through sediment samples that indicated the coast’s seismic past, taken from the sea floor off the coast of Vancouver Island. Therefore, scientist were able to outline that earthquakes occur every 500 to 1000 years.The risk for a possible megathrust earthquake to happen is increasing and it is coming faster than predicted because the stress hasn’t been released recently and the Juan de Fuca and the North American Plates are constantly moving. Right now, Vancouver Island has been tilted higher and squeezed by a few centimetres eastward every year. In the next 50 years, when the strain released, an earthquake called the “Big One” will rip down the west coast from British Columbia to northern California,

California, and thus San Francisco, lies on the San Andres fault. The earthquake was caused when this fault suddenly shifted, with the rupture spreading for a total of 476 kilometres in northward and southward direction. “This fault is a continental transform fault, which forms part of the tectonic boundary between the North American Plate and the Pacific Plate.” (1906 Earthquake: How long was the 1906 Crack? USGS Earthquake Hazards Program – Northern California, Accessed September 3, 2006). 1 The distance of the fault is of about 1300 kilometres, which runs the length of California from Cape Mendocino in the north to the Salton Sea in the south. Geologists have estimated that the fault moved as quickly as 2.74 kilometres per second. The San Andreas Fault, the source of this disaster, lies ten miles or deeper, at the meeting point of two tectonic plates, the Pacific and the North American. “The right-lateral strike-slip fault is characterized by mainly lateral motion in a dextral sense, where the western plate (Pacific plate) moves northward relative to the eastern plate (North American

Large magnitude earthquakes occur on plate boundaries and can produce hazards such as movement along faults, landslides, and tsunamis. In North America, the western coast is an active margin, meaning that it is home to earthquakes and

Megathrust earthquakes are defined as interplate earthquakes caused by one tectonic plate being forced under another in a subduction zone. During the lifetime of a subduction zone, two plates are constantly moving towards each other, and due to the great amount of friction, these plates get “stuck” in various areas 2 (fig 1). Due to the build-up of stress in these areas, the plates eventually unlock and release a great amount of energy, resulting in a megathrust earthquake2.

One of the most significant earthquakes to hit the San Fernando Valley in the past was the 1971 San Fernando/ Sylmar earthquake. On February 9, 1971 at about 6 o’clock the cities of San Fernando and Sylmar experienced an earthquake that ruptured along the Sierra Madre Fault Zone (Oakeshott, Gordon B). The epicenter of this earthquake was reported to be in the San Gabriel Valley Mountains above the valley. The citizens of both cities felt tremendous shaking. The magnitude of the earthquake was measured as a 6.6 on the Richter scale and the shaking had the intensity of a level 11 (extreme) on the Modified Mercalli system (U.S. Geological Survey). The shaking of this 6.6 magnitude earthquake lasted about 12 seconds with a very strong ground motion. The source of this faulting was located about five miles to the north of the San Fernando valley. The surface faulting of this earthquake was reported to be seen along the surface of the San Fernando fault zone from a point south of Sylmar, the faulting stretched 6 miles more as far as east to the little Tujunga Canyon, also more surface faulting was reported more east as well. In total the maximum surface rupture was 12 miles and the amount of slip was about 6 feet (U.S. Geological Survey). The type of fault scientist label this earthquake to be was an oblique-slip or also known as a thrust. The depth of this earthquake was 13km (8.1 mi) and the peak acceleration was when it reached the Pacoima dam having the speed of 1.25g (U.S.

Large magnitude earthquakes occur on plate boundaries and they can produce hazards such as movement along faults, landslides, and tsunamis if the earthquake occurs close to a large enough body of water. In North America, the western coast is an active margin, meaning that it is home to earthquakes and volcanoes, a physical manifestation of the plate activity occuring. On November 3rd, 2002, in South-Central Alaska, a 7.9 magnitude earthquake ruptured along three faults; the Susinta Glacier, Denali, and Totschunda faults (Eberhart-Phillips et al., 2003). The seismic hazards associated with this event included a few large aftershocks and liquefaction, which is when saturated soil losses its strength and behaves like a liquid

The 9.0 magnitude Indian Ocean earthquake was caused by subduction under the Indian Ocean. Earthquakes are usually caused by convection currents leading to subduction/convergent currents. Convection currents is caused by magma rising from the deepest part of the earth, then slowly cooling, sinking again then re-heating, then rising upwards basically repeating the rising and cooling then re-heating cycle over and over again. The plates are separated from each other and they move apart, the plates then obviously hit another plate right next to it causing subduction. This earthquake was caused on the Oceanic crust, in the Indian Ocean, creating tsunamis that caused disasters and thousands of life loss throughout the Indian Ocean basin. The

Scientist are struggling to come up with a widely accepted model that will explain the role of non-vertical strike-slip fault segments, crustal movement and deformation within Pacific –North American plate boundary. Multiple methods of analysis are being used; some of which are described below.

It’s recognized as the second deadliest earthquake in New Zealand following the 7.8 Hawkes bay Earthquake (Kaiser et al, 2012). The earthquake was first thought to be an aftershock of the 7.1 Darfield earthquake of September 2010 at the eastern edge. This was an area that originally was of a low earthquake occurrence rate since prior to 2011 there was no knowledge of a fault’s existence thus catching the New Zealand citizens off-guard. The Christchurch earthquake resulted in 185 casualties affecting more than 300,000 people (Kaiser et al, 2012). The earthquake first made contact with in the South Islands, only 10 km away from the center of Christchurch. Ground motions were unusually large near Christchurch measuring 2.2 g and 1.7g at the epicenter, the point directly above