EARTHQUAKES

WHAT IS AN EARTHQUAKE?

• a series of vibrations induced in the earth's crust by the abrupt rupture and rebound of rocks in which elastic strain has been slowly accumulating. http://www.dictionary.com/browse/earthquake

LOMA PRIETA EARTHQUAKE

• Oct 17, 1989 at 5:04:15 p.m.
• Magnitude 6.9 earthquake
• Epicenter located near Loma Prieta peak in the Santa Cruz Mountains , approximately 14km (9mi) northeast of Santa Cruz and 96km (60mi) south-southeast of San Francisco.
• This major earthquake caused 63 deaths, 3,757 injuries, and an estimated $6 billion in property damage.
• About 15 secs
• how did it happen? The Pacific and the Northern American suddenly slipped on the San Adreas Fault.
• Magnitude 6.9

WHAT CAUSES DAMAGE AND DESTRUCTION IN AN EARTHQUAKE?

• the shaking of the ground strikes with no warning and sometimes the shaking can even be felt hundreds of miles away.
• Because of the shaking things tend to break and fall and crack things.
• When did seismic studies begin? 1885

HOW HAVE SEISMIC STUDIES IMPROVED OUR ABILITIES TO SURVIVE EARTHQUAKES?

• losses can be reduced through documenting and understanding how structures respond to earthquakes.

WHY ARE THERE SEVERAL SCALES TO MEASURE EARTHQUAKES?

• Each scale has a different purpose.
• moment magnitude scale and is preferred because it works over a wider range of earthquake sizes and is applicable globally
• mercalli scale uses the observations of the people who experienced the earthquake to estimate its intensity.
• ritcher scale used a formula based on amplitude of the largest wave recorded on a specific type of seismometer and the distance between the earthquake and the seismometer.

SAN FRANCISCO EARTHQUAKE

• April 18, 1906 5:12 a.m.
• one of the most significant earthquakes of all time.
• More than 3,000 people died
• The total length is 296 miles (477 kilometers)
• Lasted about 45-60 seconds

FUTURISTIC IDEAS

• make sure everybody knows what to do to be as safe as possible when an earthquake comes their way.
• Improve the Seismic Scales

SIMILARITIES

• the same seismograph instrument at Gottingen, Germany was operating during both earthquakes.

DIFFERENCES

• 1989 registered - 7.0M / 1906 registered - 7.8M
• Loma Prieta lasted about 15 seconds / San Francisco lasted about 45-60 seconds.
• Most of the damage happened after 1906

Resources
https://earthquake.usgs.gov