ABAG Earthquake Info

	ABAG Earthquake Info Kids Zone

	A Quiz, Puzzles and Answers to Your Common Earthquake Questions...

Test your earthquake knowledge !

Earthquake Quiz

Earthquake Home Hazards

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Emergency Car Kit
Transportation Options
Earthquake Terms
Tsunamis
Home Hazard Hunt

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Question - What are earthquakes? Check out this interactive web site developed by JPL/NASA with the Southern California Earthquake Center (SCEC).

Question - HOW are earthquakes measured? Check out this site run by the California Geological Survey.

Question - What is the difference between the HYPOCENTER and the EPICENTER?
Earthquakes occur when two pieces of the earth snap past each other along a fault. That fault is actually a crack that extends deep into the earth. The HYPOCENTER is the point where the earthquake rupture begins, usually deep below the surface on this fault. The EPICENTER is the point on the surface directly above the hypocenter.

Question - What was the largest earthquake?
It depends on how you measure size. In terms of deaths, it was the January 23, 1556 earthquake in Shensi, China, where approximately 830,000 people were killed. Magnitude wasn't used as a measure of size until the last 100 years or so. An earthquake that had a surface-wave magnitude of about 8.7 occurred on June 12, 1897 in Assam, India. An 8.6 surface magnitude earthquake occurred on Sept. 10, 1899 in Yakutat Bay, Alaska (with no reported deaths), while an 8.6 surface magnitude earthquake occurred on March 28, 1964 (nick-named the Good Friday Earthquake) in Alaska, killing only 131 people.

By comparison, the Loma Prieta earthquake in the Santa Cruz Mountains of the Bay Area on October 17, 1989 was only a surface-wave magnitude 7.0 event (moment magnitude 6.9), killing 63-67 people and causing 3,757 serious injuries. That "moderate" earthquake made over 16,000 housing units (homes, apartment units, condo units) uninhabitable, closed 142 roads, and resulted in $6 billion in documented damage.

Question - What are the most significant earthquakes that have affected California? Check out this table prepared by the U.S. Geological Survey that lists significant California, Baja California, and Nevada earthquakes from 1769 until the present.

Question - WHERE do earthquakes occur? Check out this site run by the U.S. Geological Survey.

Question - WHY do earthquakes occur? Check out the information on another part of the site run by the U.S. Geological Survey.

Question - What type of seismic waves tend to cause the most damage?
More specifically, do the P or S - both "body" waves within the rocks - or surface waves cause more damage?

P waves typically cause windows to rattle and feel like a truck bumping a building. Next, the S waves arrive and shake the ground both horizontally (side-to-side) and vertically (up-and-down), causing far more damage to buildings. There are also two types of surface waves, which tend to arrive last. In addition, the horizontal portion of the S waves causes more damage than the vertical portion (component).

Typically, buildings are designed to "stand up" and resist gravity - a vertical acceleration. The horizontal components of shaking (just as with wind) have the potential to cause more damage. However, newer buildings in "earthquake country" are designed to withstand this shaking component, without killing people. In spite of this, the buildings can still be heavily damaged and may not be able to be used for days, weeks, or months after the earthquake.

Question - Do you have any pictures of earthquake-proof homes?
No building can be "earthquake proof" - but they can be made "earthquake resistant." Older housing can be retrofitted to be more earthquake resistant. Some examples of problem homes and resistent homes and apartments are provided in the slide shows in the mitigation section of our site.

Question - Do you have any pictures of earthquake damage to roads?
There are several in our "Riding Out Future Quakes" slide show.

Question - Is technology a part of adapting to earthquakes?
Technology is extremely important in the way our buildings and other structures are designed. The structural engineering community learns from earthquakes and corrects building and structure design to take into account those new lessons. Thus, our new highway bridges and interchanges are not built the same way they were 50 years ago - or even 20 years ago. AND we are spending billions "retrofitting" those older structures to the newer design standards. Throughout this process, we use computer technology to model shaking and other hazards, as well as to test how revised designs will withstand shaking.

Question - What is a tsunami?
A tsunami is sometimes called a "tidal wave." However, it has to do with earthquakes, not tides, so the "proper" name is tsunami. A tsunami is a great wave originating in the ocean due to an abupt change in the ocean floor due to underwater fault rupture or landslides (typically triggered by earthquakes). Thus, the 1964 Alaska earthquake trigged a tsunami that flooded and heavily damaged coastal northern California near Cresent City.

Question - Are there any other cool web sites for kids?
There is an interactive web site developed by the Federal Emergency Management Agency (FEMA).

The Exploratorium's Earthquake site is also wonderful.

ABAG, the Association of Bay Area Governments, is the regional planning and services agency for the nine-county San Francisco Bay Area.

This page was last updated 4/13/04.