Measuring and Predicting Earthquakes Objectives: Describe how to find an earthquake epicenter. Describe the different magnitude scales and what the numbers for magnitude mean. Describe how earthquakes are predicted and why the field of earthquake prediction has had little success.

Measuring Magnitude Wave motions from earthquakes are recorded as seismograms using seismographs. Ground motions from earth quakes are recorded using electronic motion detectors called seismometers.

Finding the Epicenter Step 1: Scientists determine the epicenter distance from 3 different seismographs. Step 2: Scientists draw a circle with a radius equal to the distance from the epicenter for each of the 3 seismograph locations. Animation: Great explanation and graphics of how to locate epicenter http://www.youtube.com/watch?v=dx4OqT0PYnU

Earthquake Intensity Mercalli Intensity Scale Describes earthquakes in terms of what nearby resident felt and the damage done to nearby structures Richter Magnitude Scale (Logarithmic scale) Uses a seismometer to measure the largest jolt of energy released by the earthquake Moment Magnitude Scale (Logarithmic scale) Measures the total amount of energy released by an earthquake. Animation: Richter vs Moment Scale http://www.ck12.org/flx/render/embeddedobject/1428

MERCALLI VS. RICHTER

ISOSEISMIC MAPS show the distribution of intensities Loma Prieta Earthquake 1989 Connects areas of with the same Modified Mercalli number Areas are colored according to Modified Mercalli number

Predicting Earthquakes The “where” is easy to predict. The “when” and “magnitude” are not easy to predict.

EARTHQUAKE DAMAGE Most caused by SURFACE waves (arrive last)

Earthquake Damage Building damage

Earthquake Damage Liquefaction when a solid (sand and soil) becomes saturated with water and acts like a heavy liquid Results in a loss of soil strength & the ability of the soil to support weight (Landslides)