Earthquake Hazards

Predictions• Based on 2 factors:

– Earthquake history in the area (only narrows down to a decade or a few years)

– Rate at which strain/stress builds up in the rocks (cracks or bulging)

Result:Not much direct warning! Before and After Earthquake

Presidential Palace in Port-au-Prince, Haiti (2010)

Left: Photo taken prior to the earthquake. Low income housing- unreinforced masonry.

-Many people live in structures that are vulnerable to earthquake shaking.- Most buildings can withstand up-and-down movements, but the largest movements at Earth’s surface are side-to-side.

Below: After

BBC

Magnitude 7.0 HAITIMagnitude 7.0 HAITITuesday, January 12, 2010 at 21:53:09 UTC Tuesday, January 12, 2010 at 21:53:09 UTC

Structural Collapse

Aftershocks• Even though the major strain between two plates is released by

the initial quake, their touching edges still need to adjust to new positions. The edges may not be able to pass each other smoothly, and this additional realignment creates smaller shocks.

• Usually occur within the next two days (but can be longer) and still have the potential for serious damage•Ex. Nepal 2015 earthquake was a 7.8 with an aftershock of 7.3 two weeks later, triggering more avalanches and landslides.

Tsunamis• Enormous waves that occur when the sea floor

abruptly deforms due to an earthquake (NOT tides!) and vertically displaces the overlying water

• Speed is greatest in deep water, but as it slows in shallow water its height drastically increases

• Tsunami Explanation• Japan's Tsunami Caught on Camera

Projected travel times for the arrival of the tsunami waves across the Pacific.

Nearby the earthquake there are only minutes to evacuate. However, in many other regions there is advance warning.

A tsunami map shows projected travel times for the Pacific Ocean. This map indicates forecasted times only, not that a wave traveling those distances has actually been observed.. NOAA

Magnitude 9.0 NEAR THE EAST COAST OF HONSHU, JAPANMagnitude 9.0 NEAR THE EAST COAST OF HONSHU, JAPANFriday, March 11, 2011 at 05:46:23 UTC Friday, March 11, 2011 at 05:46:23 UTC

Earthquake Safety (from FEMA)• Check for Hazards in the Home (ex. loose shelves)• Develop an Emergency Communication Plan• If indoors

– DROP to the ground; take COVER by getting under a sturdy table or other piece of furniture; and HOLD ON on until the shaking stops. If there isn’t a table or desk near you, cover your face and head with your arms and crouch in an inside corner of the building.

– Stay away from glass, windows, outside doors and walls, and anything that could fall, such as lighting fixtures or furniture.

• If outdoors– Stay there and move away from buildings, streetlights, and utility

wires.– Once in the open, stay there until the shaking stops. The greatest

danger exists directly outside buildings, at exits, and alongside exterior walls.

• Expect aftershocks.• Be aware of possible tsunamis if you live in coastal areas.