1. Ground shaking intensity is defined as the severity of ground motion, i.e. displacement, during an earthquake and is assessed using the Modified Mercalli Intensity Scale (MMI). This scale is a good indicator on the effects and earthquake has on the environment and its population. It is based on three features:
People’s perception
Building performance
Changes in the natural environment
The MMI is often associated to Peak Ground Acceleration (PGA), which is used to quantify the severity of ground shaking as shown in Table 1.
The intensity of an earthquake is a qualitative measure of the shaking at a location and it usually depends on:
The Magnitude of an earthquake
Distance from the fault
Local Geology
These will all affect the way in which seismic waves will propagate through the ground and therefore will be responsible for all the subsequent event which will occur as a result of the earthquake.
Subsidence is a result of earthquake shaking. As the ground shakes, unconsolidated sediments lose their bearing strengths and the ground “shifts” downwards relative to sea level and this resulted in liquefaction and landslides and flooding. Subsidence can also occur as a result of downward displacement on one side of a fault which may sometimes affect large areas of land.
The 4th of September 2010 Darfield event generated a magnitude 7.1 earthquake with a MMI of 9. This earthquake resulted in extensive liquefaction and differential subsidence which was located close to major streams and rivers around Christchurch.
The 22nd of February 2011 Christchurch City event created a magnitude 6.3 earthquake with a MMI of 9. This earthquake occurred within 10 kilometres of the city at a shallow depth of 5 kilometres. This cau...
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...l change and liquefaction in the Avon-Heathcote Estuary. Report No. U11/13, Christchruch: Environment Canterbury Regional Council, 2011.
Quigley, M. Van Dissen, R., Villamor, P., Litchfield, N., Barrell, D., Furlong, K., Stahl, T., Duffy, B., Bilderback, E,. Noble, D., Townsend, D., Begg, J., Jongens, R., Ries, W., Claridge, J., Klahn, A., Mackenzie, H., Smith, A., Hornblow, S., Nicol, R. “Surface rupture of the Greendale Fault during the Mw 7.1 Darfield (Canterbury) earthquake, New Zealand: Initial Findings.” Bulletin of the New Zealand Society for Earthquake Engineering 43:4 (2010): 236-242.
SC Cox, HK Rutter , A Sims , M Manga , JJ Weir , T Ezzy , PA White , TW Horton & D Scott (2012). “Hydrological effects of the Mw 7.1 Darfield (Canterbury) earthquake, 4 September 2010, New Zealand.” New Zealand Journal of Geology and Geophysics 55:3 (September 2012): 231-247.
Gabrysch, R. K. and C.W. Bonnett. "Land Surface subsidence at Seabrook, Texas US." Geological Survey 1977: 21-74. 48 pp.
Earthquakes are a natural part of the Earth’s evolution. Scientific evidence leads many geologists to believe that all of the land on Earth was at one point in time connected. Because of plate tectonic movements or earthquakes, continental drift occurred separating the one massive piece of land in to the seven major continents today. Further evidence supports this theory, starting with the Mid-Atlantic ridge, a large mass of plate tectonics, which are increasing the size of the Atlantic Ocean while shrinking the Pacific. Some scientists believe that the major plate moveme...
Earthquakes play a major role into understanding the composition and materials that exist within the Earth (Merali and Skinner, 2009, p.252). Earthquakes are the main source of insight into the inner workings of the earth, due to the nature of the seismic waves they produce. P and S waves are reflected and refracted at different boundaries within the earth, and this enables seismologists to make inferences about the internal composition and structural of planet Earth. (Merali and Skinner, 2009, p.252).
Heller, Arnie. "The 1906 San Francisco Earthquake." Science & Technology (2006): 4-12. Web. 8 May 2014.
One of the worst natural disasters in United States history to this date occurred almost 109 years ago. On April 18, 1906 at 5:15am in San Francisco, California, the earthquake of San Francisco occurred hitting between 7.9 and 8.3M on the Richter scale. The San Andreas Fault, which is about 600 miles long, running from the Gulf of California to Cape Mendocino and is an active strike-slip fault, cut through the continental lithosphere to cause the San Francisco Earthquake of 1906. An earthquake is a trembling or shaking of the ground produced by movements along a fault (Strahler, 2012). After the tension is released at a critical point, the fault or tectonic plate slips and relieves the strain and creates the seismic waves, which radiates out in all directions causing the shaking of the surface.
Earthquakes are best described as a shaking or vibration of the ground caused by breaking of rock. Sometimes they are very strong and other times you would hardly notice them. This shaking occurs when stress that builds up in the crust is suddenly released as the crust breaks free and/or slides against the other pieces of crust. Earthquakes may also be thought of as the breaking of a popsicle stick by applying pressure to both ends at the same time. Should you try this experiment , you will feel the pressure build up as you apply more force until the stick snaps. When the stick snaps you will feel an instant of pain at your fingers as the stress reduces and energy waves move throughout the stick. When the earth's crust is placed under similar types of stress, binding as the stress builds, it will also snap and release the energy into the surrounding rocks, 'ooch'. Thinking about earthquakes will become more clear if you try another experiment.
"USGS: Geological Survey Bulletin 1347 (Earthquakes)." USGS: Geological Survey Bulletin 1347 (Earthquakes). Web. 20 Feb. 2014.
Debris from the Earthquake falls into the ponds,lakes, and rivers. The spilling of hazardous chemicals makes its way to the water supply as well. This kills wildlife that live in the water system, as well as the ones that use it for water or their food supply.
benchmark for the future, and integrated investigation into the effects of earthquakes in the U.S.
The west coast of the islands is on the edge of a continental shelf created by ancient volcanic movement (Broadhead 5) .This volcanic activity is due to plate tectonic movement which also created the numerous amounts of earthquakes on the island. Compared to the rest of British Columbia, Haida Gwaii has the most earthquake activity (Broadhead 5), the last of which being in a magnitude of 7.7 on t...
The epicenter of the earthquake in Alaska was about 10km east of the College Fiord, approximately 90km west of Valdez and 120km east of Anchorage, Alaska largest city. The earthquake was felt about 1,300,000 square kilometers away from the epicenter. (Christensen, Doug PhD.) About 30 kilometers deep, the first slip occurred under northern Prince William Sound, and an 800 kilometer rupture in the rocks extended horizontally, roughly parallel to the Aleutian trench. (Bolt) The cause of this massive earthquake was the vertical displacement of northwest motion of the Pacific plate. Also, it was estimated that about 200,000 square kilometers of the crust were deformed, making this the greatest area of vertical displacement ever measured. (Bolt)
Living in Bangladesh, we have seen quite disastrous mudslides from the past few years. Mudslide is also called a landslide or a land slip. It is a downward mass movement of earth or rock on unstable slopes, including many forms resulting from differences in rock structure, coherence of material involved, degree of slope, amount of included water, extent of natural or artificial undercutting at the base of the slope, relative rate of movement, and relative quantity of material involved. There are numerous facts that can cause a mudslide and there are also numerous effects that it can cause us.
They are the earth’s crust; they move very slowly every year. As the tectonic plates slide over each other they cause earthquakes. Earthquakes produce various damaging effects this includes damage to structures of buildings, bridges and other standing formations which then...
... although we may never be able to understand exactly what soil failures can occur when a natural disasters take place, as time goes on and testing instruments and materials advance we will hopefully have a better understanding of what we can do to avoid soil failures and come up with a better and more sufficient method of improving the soils structure and strength permanently. While researching the information for this report I feel I have a much better understanding for construction geo-technics and foundations especially regarding the deformation, liquefaction and pile information related to this specific event. I hope to carry the information I have learned from this event into the construction field and apply them towards an authentic project that’s taking place and know that the information, regarding soils, I have given input on will be precise and accurate.
Earthquakes belong to the class of most disastrous natural hazards. They result in unexpected and tremendous earth movements. These movements results from dissemination of an enormous amount of intense energy in form of seismic waves which are detected by use of seismograms. The impact of earthquakes leaves behind several landmarks including: destruction of property, extensive disruption of services like sewer and water lines, loss of life, and causes instability in both economic and social components of the affected nation (Webcache 2).