earthquakes

Submitted By: Name: Sumesh Goyal. Roll no: RH4001 A15 Section:H4001 Reg. no:11007038:

EARTH QUAKE Submitted By: Name: Sumesh G oyal. Roll no: RH4001 A15 Section:H4001 Reg. no:11007038

What are Earthquakes?:

What are Earthquakes? The shaking or trembling caused by the sudden release of energy Usually associated with faulting or breaking of rocks Continuing adjustment of position results in aftershocks

What is the Elastic Rebound Theory?:

What is the Elastic Rebound Theory ? Explains how energy is stored in rocks Rocks bend until the strength of the rock is exceeded Rupture occurs and the rocks quickly rebound to an undeformed shape Energy is released in waves that radiate outward from the fault

Slide 4:

The Focus and Epicenter of an Earthquake The point within Earth where faulting begins is the focus, or hypocenter The point directly above the focus on the surface is the epicenter

Slide 5:

Seismographs record earthquake events At convergent boundaries, focal depth increases along a dipping seismic zone called a Benioff zone

Where Do Earthquakes Occur and How Often?:

Where Do Earthquakes Occur and How Often? ~80% of all earthquakes occur in the circum-Pacific belt most of these result from convergent margin activity ~15% occur in the Mediterranean-Asiatic belt remaining 5% occur in the interiors of plates and on spreading ridge centers more than 150,000 quakes strong enough to be felt are recorded each year

The Economics and Societal Impacts of EQs:

The Economics and Societal Impacts of EQs Damage in Oakland , CA, 1989 Building collapse Fire Tsunami Ground failure

What are Seismic Waves?:

What are Seismic Waves? Response of material to the arrival of energy fronts released by rupture Two types: Body waves P and S Surface waves R and L

Body Waves: P and S waves:

Body Waves: P and S waves Body waves P or primary waves fastest waves travel through solids, liquids, or gases compressional wave, material movement is in the same direction as wave movement S or secondary waves slower than P waves travel through solids only shear waves - move material perpendicular to wave movement

Surface Waves: R and L waves:

Surface Waves: R and L waves Surface Waves Travel just below or along the ground’s surface Slower than body waves; rolling and side-to-side movement Especially damaging to buildings

How is an Earthquake’s Epicenter Located?:

How is an Earthquake’s Epicenter Located? Seismic wave behavior P waves arrive first, then S waves, then L and R Average speeds for all these waves is known After an earthquake, the difference in arrival times at a seismograph station can be used to calculate the distance from the seismograph to the epicenter.

How is an Earthquake’s Epicenter Located?:

How is an Earthquake’s Epicenter Located? Time-distance graph showing the average travel times for P- and S-waves. The farther away a seismograph is from the focus of an earthquake, the longer the interval between the arrivals of the P- and S- waves

How is an Earthquake’s Epicenter Located?:

How is an Earthquake’s Epicenter Located? Three seismograph stations are needed to locate the epicenter of an earthquake A circle where the radius equals the distance to the epicenter is drawn The intersection of the circles locates the epicenter

How are the Size and Strength of an Earthquake Measured?:

How are the Size and Strength of an Earthquake Measured? Intensity subjective measure of the kind of damage done and people’s reactions to it isoseismal lines identify areas of equal intensity Modified Mercalli Intensity Map 1994 Northridge, CA earthquake, magnitude 6.7

How are the Size and Strength of an Earthquake Measured?:

How are the Size and Strength of an Earthquake Measured? Magnitude Richter scale measures total amount of energy released by an earthquake; independent of intensity Amplitude of the largest wave produced by an event is corrected for distance and assigned a value on an open-ended logarithmic scale

What are the Destructive Effects of Earthquakes?:

Ground Shaking amplitude, duration, and damage increases in poorly consolidated rocks What are the Destructive Effects of Earthquakes?

Can Earthquakes be Predicted?:

Can Earthquakes be Predicted? Earthquake Precursors changes in elevation or tilting of land surface, fluctuations in groundwater levels, magnetic field, electrical resistance of the ground seismic dilatancy model seismic gaps

Can Earthquakes be Predicted?:

Can Earthquakes be Predicted? Earthquake Prediction Programs include laboratory and field studies of rocks before, during, and after earthquakes monitor activity along major faults produce risk assessments

Can Earthquakes be Controlled?:

Can Earthquakes be Controlled? Graph showing the relationship between the amount of waste injected into wells per month and the average number of Denver earthquakes per month Some have suggested that pumping fluids into seismic gaps will cause small earthquakes while preventing large ones

Designing Structures To Perform Well During an Earthquake: There are different factors that affect how structures perform during an earthquake. Important Design Considerations. When you design buildings, there are a number of factors you need to consider: Shape of the building: different shaped buildings behave differently. Geometric shapes such as a square or rectangle usually perform better than buildings in the shape of an L, T, U, H, +, O, or a combination of these. Various materials used to construct the building(s) can be used (alone or in combination): steel, concrete, wood, brick. Concrete is the most widely used construction material in the world. It is comprised of sand, gravel, and crushed stone, held together with cement. Each material behaves differently. Ductile materials perform better than brittle ones. :

Building Structure Exercise Designing Structures To Perform Well During an Earthquake: There are different factors that affect how structures perform during an earthquake. Important Design Considerations. When you design buildings, there are a number of factors you need to consider: Shape of the building: different shaped buildings behave differently. Geometric shapes such as a square or rectangle usually perform better than buildings in the shape of an L, T, U, H, +, O, or a combination of these. Various materials used to construct the building(s) can be used (alone or in combination): steel, concrete, wood, brick. Concrete is the most widely used construction material in the world. It is comprised of sand, gravel, and crushed stone, held together with cement. Each material behaves differently. Ductile materials perform better than brittle ones.

Height of the building different heights shake at different frequencies. Soil beneath the building. Regional topography. Magnitude and duration of the earthquake. Direction and frequency of shaking. The number of earthquakes the building has previously had and the kinds of damage suffered, if any. :

Height of the building different heights shake at different frequencies. Soil beneath the building. Regional topography. Magnitude and duration of the earthquake. Direction and frequency of shaking. The number of earthquakes the building has previously had and the kinds of damage suffered, if any.

What Can You Learn by Constructing Buildings? The effect of the different variables on building performance during a simulated earthquake. Ways to strengthen the buildings What physical forces are at work during an earthquake. :

What Can You Learn by Constructing Buildings? The effect of the different variables on building performance during a simulated earthquake. Ways to strengthen the buildings What physical forces are at work during an earthquake.

Making Wood Frame Structures :

Materials: Popsicle sticks, clay, styrofoam piece, and a shake table for testing Procedure: Construct one or two story frame buildings using popsicle sticks with clay for jointing. Let the building sit until the clay is cool and stiff. If desired, use the styrofoam piece to make a foundation for the building. Cut the styrofoam the same size as the external perimeter of the house with a cutout for a basement. Try setting the building on the styrofoam or fastening the building to the styrofoam with clips, tacks, or an adhesive. Test your model structure, like engineers often do, on a shake table or seismic simulation equipment to see how it performs during a simulated earthquake. Strengthening Your Building: Try cross or diagonal bracing to further stabilize your building. Cross-bracing means you put in vertical "X' shaped braces between the popsicle stick walls. Try different materials for your crossbraces and see which works best: popsicle sticks, kite string, straws. Making Wood Frame Structures

Simulating Masonry (Brick, Stone or Adobe Structures) :

Materials: Sugar cubes (1 box per structure), peanut butter, frosting or doublesided tape, piece of Styrofoam, cardboard, and aluminum window screen scraps. Procedure: Construct one and two story rectangle and L-shaped buildings on Styrofoam bases, using sugar cubes for bricks, cardboard for the floor and roof, peanut butter, and frosting or double-sided tape for mortar. Again, try setting the building on the Styrofoam or somehow connecting it to the Styrofoam. Then test your model structures on shake tables to see how they perform during a simulated earthquake. Which are more stable, one or two story structures? How did the right angle in the Lshaped building effect the stability of the structure? Strengthening Your Building: Carefully cut pieces of screen smaller than the size of each of the walls. Spread a very thin layer of peanut butter or frosting on each screen and carefully attach the screen to each of the inside walls of the first story. Reinforce the corners with extra peanut butter from inside. This is a model of a one story reinforced masonry structure. Try different sized screen fine and widely spaced. How do the buildings respond now when shaken? Simulating Masonry (Brick, Stone or Adobe Structures)

Steel Frame Structures:

Materials: Pipe cleaners, t-pins, Styrofoam piece, cardboard/ paper pieces (optional) Procedure: Construct a model of a modern high-rise steel framed city building using pipe cleaners. Bend the end of one pipe cleaner around the end of the other. Do not twist the ends together. Attach each model to a Styrofoam base with T pins. Test it on a shake table to see how it performs during a simulated earthquake. Adding the Walls: A steel frame structure looks sort of like a jungle gym. However, the finished building has walls and windows. Make cardboard or paper walls and add them to your structure. How does it perform on the shake table? Try other materials for the walls and cross-bracing to strengthen the structure. Steel Frame Structures

Thank You For Your Attention:

Thank You For Your Attention