Earthquake overview and Earthquake Engineering activity What is

Earthquake overview and Earthquake Engineering activity

What is an Earthquake?

Pattern of earthquakes defines the boundaries of tectonic plates There about 23 major plates

Three types of interactions between plates as they move around: Sliding past one another - transform boundary Running into one another - convergent boundary Moving away from one another - divergent boundary

Where are earthquakes likely to occur? • Tectonic development of the New Madrid rift complex, Mississippi embayment, North America: • A rift was splitting apart the North American continent 600 million years ago • Rifting stopped • The continent has been under compression for at least 150 million years • The ancient faults may have been reactivated but are moving in the opposite sense by Lawrence W. Braile, William J. Hinze, G. Randy Keller, Edward G. Lidiak, and John L. Sexton; 1986; in Tectonophysics, Volume 131 (1986).

How strong will the ground shake? • http: //quake. wr. usgs. gov/prepare/factsheets/New. Madrid • U. S. Geological Survey Fact Sheet-168 -95 1995

What determines the level of shaking? • Magnitude – More energy released • Distance – Shaking decays with distance • Local soils – amplify the shaking

P and S Waves

• It is estimated that there are 500, 000 detectable earthquakes in the world each year. 100, 000 of those can be felt, and 100 of them cause damage. http: //earthquake. usgs. gov/learning/facts. php

• The magnitude of an earthquake is a measured value of the earthquake size. The magnitude is the same no matter where you are, or how strong or weak the shaking was in various locations. The intensity of an earthquake is a measure of the shaking created by the earthquake, and this value does vary with location. http: //earthquake. usgs. gov/learning/facts. php

Richter magnitude scale • Because of the logarithmic basis of the scale, each whole number increase in magnitude represents a tenfold increase in measured amplitude; as an estimate of energy, each whole number step in the magnitude scale corresponds to the release of about 31 times more energy than the amount associated with the preceding whole number value.

Taken from: http: //www. sdgs. usd. edu/publications/maps/earthquakes/rscale. htm

The 1906 San Francisco Earthquake (M~7. 8) ~3 m right lateral offset on the San Andreas fault

The 1906 San Francisco Earthquake (M~7. 8) San Francisco after the Earthquake and fire.

The 1906 San Francisco Earthquake (M~7. 8) Comparison of fault lengths for selected significant events on the San Andreas.

Soft first story failure

Building shifted off foundation

Olive View Hospital, 1971 S Fernando Earthquake

Olive View Hospital, 1971 S Fernando Earthquake

Dec. 26, 2003 M 6. 6 Earthquake, Bam, Iran, ~80% of buildings destroyed

Earthquake Engineering Activity: • Supplies: (per group) – 1 sheet of card stock (cut into 1” wide 8 “ long strips) – 1 3 x 5 note card – 1 meter of tape – 1 tray – 1 golf ball – Ruler

Earthquake Engineering Activity: • Rules: – Must use only the materials provided – Structure must be 15 cm in height (the bottom of the ball must be 15 cm off the tray) – Structure must hold the golf ball (the ball cannot be taped down)

http: //www. earthquakecountry. info/roots/steps. html

Magnitude Earthquake Effects Estimated Number Each Year 2. 5 or less Usually not felt, but can be recorded by seismograph. 900, 000 2. 5 to 5. 4 Often felt, but only causes minor damage. 30, 000 5. 5 to 6. 0 Slight damage to buildings and other structures. 500 6. 1 to 6. 9 May cause a lot of damage in very populated areas. 100 7. 0 to 7. 9 Major earthquake. Serious damage. 20 8. 0 or greater Great earthquake. Can totally destroy communities near the epicenter. One every 5 to 10 years