Loose granular sediment and/or soil must be present, enough water to saturate sediment and/or soils, and ground shaking must be sufficiently intense that grains within water saturated sediment and/or soil lose contact with each other What can happen to large structures that are built on materials that liquefy during an earthquake Expected Shaking This map builds on the map of likely earthquakes above to show how those earthquakes will shake the region. The softer the rock or soil under a site is, … The IS 875 (part 4) – 1987 deals with snow loads on roofs of the building. Shaking intensity varied from barely perceptible to completely destructive. Liquefied soil will force open ground cracks in order to escape to the surface. • Topographic effects can amplify ground motion shaking that would otherwise be expected on level ground along ridges or near the tops of slopes. In a similar fashion, the soft foundation materials at a soil site will amplify the seismic waves, which results in much more vigorous shaking than would be expected at a … Site responsed… Earthquake - Earthquake - Properties of seismic waves: At all distances from the focus, mechanical properties of the rocks, such as incompressibility, rigidity, and density, play a role in the speed with which the waves travel and the shape and duration of the wave trains. Which of the following is true about how the type of geologic material at the earth's surface will affect the the level of shaking and potential for causing damage during large earthquakes. a. the magnitude of the earthquake b. the distance from the epicenter c. the angle between the fault and the maximum principal stress direction d. the local geological conditions _____15. (2014, January 20). As an example, parts of Seattle and certain areas of downtown Olympia are built on softer ground that will amplify ground shaking during an earthquake. What types of Earth materials are most likely to amplify seismic waves and undergo liquefaction during an earthquake? Which of the following near-surface earth materials will amplify ground shaking the most? Ground shaking. Buildings respond differently to shaking depending on construction styles, materials Wood -- more flexible, holds up well The distance from the source event. 3)shaking must be sufficiently intense so grains within water contact each other. In places with certain rock compositions, this bouncing will amplify the waves, which will then cause more damage. 2)sufficient ground water. HAZUS uses predetermined NEHRP ground uses predetermined NEHRP ground Intensity of shaking also depends on type of subsurface material. Metamorphic rocks like gneiss Given that buildings are usually stronger vertically than they are laterally, which kinds of seismic waves cause the most building damage? Ground Shaking Two important local geologic factors that affect the level of shaking experienced in earthquakes are (1) the softness of the surface rocks and (2) the thickness of surface sediments. I do not believe that materials themselves, whether natural or artificial, can really amplify sound. 2. These classifi-cations are used in all figures on this and the next few pages. Mexico City, which has a population of just under 9 million people, is located directly on a large sedimentary basin with loose soil, … Much of Invercargill City is constructed on “Deep or Soft Soil” or “Very Soft Soil” that is likely to amplify ground shaking depending on whether the earthquake source is distant or nearby. Hard rocks OTOH allow energy to pass through efficiently. 5. Take a look at these seisomograms (pictures of earthquake signals) from the 1989 Loma Prieta earthquake. Which of the following factors affect the intensity of ground shaking? highly saturated area, intense ground shaking, loose granular sediment. Solid bedrock such as granite will amplify strong ground motion and increase the likelyhood of earthquake damage b. ), but shaking intense enough to cause damage is usually due to rupturing of the earth's crust known as earthquakes. Seismologist Susanne Sergeant of the British Geological Survey says: "Softer materials amplify the ground shaking." earthquake hazard maps for ground shaking amplification and liquefaction susceptibility and supersedes classifications made in 1993 and 2006. Seismic waves travel faster through hard rocks than through softer rocks and sediments. Since 1933, in the United States we have used what's called the The intensity of ground shaking depends on: conditions of the local geology influence events: solid bedrock is far less subject to intense shaking than loose sediment; Locked Faults. Ground shaking, rather than surface fault rupture, is the cause of the ... soils, such as uncompacted alluvium and artificial fill, tend to amplify and prolong ground shaking, while bedrock is less susceptible. For example, shaking at a site with soft sediments can last 3 times as long as shaking at a stable bedrock site such as one composed of granite. the softness of the rock or soil near the surface. (shaking is amplified in softer rock) the thickness of the sediments above hard bedrock. (shaking is amplified where sediments are thicker). Ground Shaking. how intense the shaking felt to people near the epicenter. process that changes solid earth material liquid-like. The two found to be most important are the softness of the ground at a site and the total thickness of The type of seismic wavegenerated, and its orientation. Eventually, shaking intensity scaleswere developed to standardize the measurements and ease comparison of different earthquakes. For example, deep unconsolidated materials can amplify earthquake waves and cause longer periods of ground shaking. (This material will greatly increase the intensity of shaking.) The second primary earthquake hazard, ground shaking, is the result of rapid ground acceleration. The amplitude of ground shaking is affected by the near-surface geology (Figure 3). Like the factors that must be in place before liquefaction can occur. on ground motions, including body wave reflections and surface wave generation at basin edges. Different maps portray different types of ground shaking information; some maps are designed to inform engineers on the design of small residential structures affected by high frequency ground motion, others are useful for designing tall buildings and long bridges that are more susceptible to longer wavelength ground shaking. Local geology and topography may amplify ground shaking at some frequencies and may de-amplify shaking at other frequencies. liquefaction. Term. What kind of material amplify ground shaking… Ground shaking is a hazard near the epicenter of an earthquake and also in areas far from the earthquake where amplification occurs. Vancouver: Nearby Georgia basin may amplify ground shaking from next quake. Different maps portray different types of ground shaking information; some maps are designed to inform engineers on the design of small residential structures affected by high frequency ground motion, others are useful for designing tall buildings and long bridges that are more susceptible to longer wavelength ground shaking. ... earthquakes occur along all three types of plate … ground types of different softness had dif-ferent levels of shaking relative to each other, the SCEC study is the first that has assigned numerical values to these effects on such a broad scale. The different types of motion in Rayleigh and Love waves. This image of the Los Angeles region combines this information to predict the total amplification expected in future earthquakes from local geologic conditions or site effects. It's just that they do so do by shaking vigorously which is not good for buildings. But they can redirect or enhance sound. In loose water-saturated sediment, liquefaction can occur causing the ground to turn to “quick sand” during earthquake shaking. Seismic waves travel at different speeds in different types … By combining observations from past earthquakes with computer-based predictions, the SCEC working group quantified how levels of ground shaking in southern California are modified by various characteristics of local geology. Earthquake. Seismological Society of America. These maps represent the intensity of shaking on rock. These all affect the way the seismic waves travel through the ground. The layering of the rocks and the physical properties of surface soil also affect wave characteristics. geological materials. As the waves pass from deeper harder to shallow softer rocks they slow down and get bigger in amplitude as the energy piles up. 4. Local soil conditions also play a role, as certain soils greatly amplify the shaking in an earthquake. The site classes range from A to E, where A represents the hardest rocks, and E the softest soils. ranges from A to E, whereby A represents hard rock that reduces ground motions from an earthquake, and E represents soft soils that amplify and magnify ground shaking and increase building damage and losses. tilt or sink into liquefied deposits. Fine-grained, sensitive materials can lose strength when shaken. Violent ground shaking is generally expected at and near the epicenter of a large earthquake; however, different types of geologic materials respond differently to earthquake waves. At least 139 people died in the states of Morelos, Puebla and Mexico following a powerful earthquake that struck central Mexico. Soft soils amplify ground shaking more than hard soils do. Shaking of the ground caused by the passage of seismic waves, especially surface waves near the epicentre of the earthquake are responsible for the most damage during an earthquake. Loose soils are known to amplify shaking and damage from earthquakes in a process called liquefaction, where the ground takes on a soupy character. The intensity of shaking depends on several factors: 1. Ground shaking. Shaking of the ground caused by the passage of seismic waves, especially surface waves near the epicentre of the earthquake are responsible for the most damage during an earthquake. Bands of highest shaking generally follow major faults, but shaking levels are also influenced by the type of materials underlying an area — soft soils tend to amplify and prolong shaking, even at great distances from a quake. If you are looking for speakers (amplification), hard cardboard or plastic works really well. If you are looking to record sound, bamboo would probably be best if you are looking to amplify your audio. The ejected material often results in flooding and may leave cavities in the soil 8. But these types of loads are considered only in the snow fall places. Molina Hutt and his co-authors used these M9 simulations to determine how much the sedimentary basin could amplify shaking and what effect this shaking could have on buildings. Earthquake – induced ground subsidence and lateral spreading Subsidence, or lowering … Earthquake Shaking Animation These computer-generated snapshots show maximum velocity of ground motion as the earthquake waves move out from the fault and travel through southern California. The "size" or strength of the source event, such as measured by various seismic magnitude scales. ScienceDaily. The 26 May 2006 magnitude 6.4 Yogyakarta earthquake south of Mt. The type of soil affects how much shaking a house experiences. 1)loose, granular sediment and/or soil must be present. There is no map yet for Vancouver and the Fraser Valley showing areas of expected ground amplification or de- … Hard bedrock experiences much less violent ground shaking than does soft sedimentary layers while loose sediments greatly amplify ground shaking. Definition. A short presentation on basin effects is presented in Chapter 4 of Bozorgnia and Bertero (2004). Snapshots are taken at 30, 60, 90, 120, 150, 180, 210, and 240 seconds after the fault starts rupturing. water present to saturate sediment and/or soil, c. Ground shaking must be sufficiently intense that grains within water saturated sediment and/or soil lose contact with each other 12. Ground shaking can be caused in various ways (volcanic tremors, avalanches, large explosions, etc. Ground shaking can vary over an area as a result of factors such as topography, bedrock type and the location and orientation of the fault rupture. The depth of the event. The M9 simulations work better than traditional ground motion models because they’re more detailed and location-specific, says Molina Hutt. … Merapi volcano: Did lahar deposits amplify ground shaking and thus lead to … When unchanged, HAZUS-MH default soil types … What types of earth materials amplify seismic waves? Soft soils amplify ground shak-ing and increase building damage and losses. But she cautioned: "At this point it's … They lose strength by liquefaction. Locations are determined using the lengths of time the seismic waves take to travel to the seismograph. Large strain energy released during anearthquake as seismic The interface between soft sediments and bedrock is where phase conversion happens (due to impedance contrast) and waves get trapped and cannot easily exit the system. Result when the confining pressure exerted by the overlying crust is enormous, causing these fractures in … Select one or more: I a. 3. List the factors that must be in place before liquefaction can occur. Un consolidated materials amplify shaking more than rocks do. S waves and surface waves 4. Now, imagine a building sitting on ground that is going through all these motions at once. Ground shaking caused by the sudden and rapid movement of one block of rock slipping past another along fractures in Earth's crust, called faults. Yellow indicates the most damaging level, with orange and red also likely to cause damage. The minimum snow load on a roof area or any other area above ground which is subjected to snow accumulation is obtained by the expression This QuickTime animation shows how seismic waves are amplified when they pass through weak or loose layers of rocks and sediment. Snow loads constitute to the vertical loads in the building. When the shaking reaches the bowl of jello, however, the waves are amplified so that the top of the jello jiggles and causes the blocks to topple.
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