Chapter 8 Section 2 Seismic Waves Waves generated

Chapter 8 Section 2 Seismic Waves: • Waves generated by an earthquake • Body waves – travel through the interior of the Earth • Surface waves- travel along the surface

P-Waves: • Push/pull waves • Caused by compression and expansion • Travel faster than S waves • Can travel through both solids and liquids

S - Waves: • Shake particles to right angle of direction • Transverse waves • Travel more slowly than P waves • Can travel through solids but NOT liquids

Surface Waves: • Caused when body wave reaches the surface • Travel slower than body waves • Much larger than body waves • Most destructive body waves

Recording Seismic Waves Seismographs: • Measured using a seismograph • Weight suspended from a string • Attached to bedrock

Seismogram: • Record of an earthquake • Shows three types of seismic waves • The stronger the earthquake the larger the waves

Measuring Earthquakes Richter Scale: • Measures the magnitude of an earthquake • Based on height of largest wave • 10 x increase wave height = 1 increase in magnitude • Only useful for small, shallow earthquakes within 500 miles of the epicenter

Moment Magnitude Scale: • Estimates the amount of energy released • Includes seismographic data, average amount of movement along the fault, the area of the surface break and the strength of the broken rock

Modified Mercalli Scale: • Rates intensity • Determined by visible damage

Locating an Earthquake • P-waves and S-waves travel at different speeds • The further the distance the longer the time interval • Use three or more locations to determine the epicenter

Steps to Locating the Epicenter: 1. Measure the time interval between the P & S waves 2. Refer to the Time Interval Graph to determine distance from epicenter 3. Draw a circle on a map locating the distance 4. Use three different seismograph stations to locate the epicenter