Earthquakes

Studying Earthquakes

Target 8- I can define seismology

• Seismology: the study of earthquakes and seismic waves

Target 9- I can describe a seismograph

• Seismograph: an instrument that records vibrations in the ground–Measures vertical and horizontal motion of

the ground– Records motion on paper and electronically

Target 10- I can define seismogram

• Seismogram: a tracing of earthquake motion that is recorded by a seismograph– P waves are recorded first– S waves are recorded second

Target 11- I can identify the location of P waves, S waves, and Surface waves on a seismogram

Target 12- I can determine the S-P Interval of a seismogram

and use that to calculate the

distance to the epicenter

• To determine the distance to an epicenter, scientists analyze the arrival times of the P waves and the S waves–The more space

between the P waves and the S waves, the farther away the earthquake occurred

Target 13- I can describe the scale used to determine magnitude

• Magnitude: a measure of the strength of an earthquake–Moment Magnitude Scale: measures an

earthquake’s strength based on the size of the area, the amount of movement, and the rigidity, of the fault that moves

Target #14- I can find the amplitude of

an earthquake on a

seismogram

• To determine magnitude of an earthquake you must find the amplitude of the S- wave– Amplitude is determined

by measuring how high above the center line the tallest S wave is on a seismogram

Target #15- I can use the distance and amplitude found using a seismogram to determine an

earthquake’s magnitudeWhat would be the magnitude of an earthquake 100 km away that produced 100 mm of amplitude? What would be the magnitude of an earthquake 60 km away that produced 2 mm of amplitude? What would be the magnitude of an earthquake 200 km away that produced 100 mm of amplitude? What would be the magnitude of an earthquake 500 km away that produced 2 mm of amplitude?