Earthquakes occur in the Earth, not on Earth’s surface. That means, if the earthquake is shallow, the shaking will be intense. If the earthquake is deep, the seismic waves attenuate, or grow weaker on their way to the surface.
Consider two separate earthquakes: they have the same magnitude, but at different depths. How does this affect shaking intensity? The 2001 M6.8 Nisqually, Washington and the 1994 M6.7 Northridge, California earthquakes had similar magnitudes, but much different intensities. The 2001 Nisqually earthquake was almost twice as deep as the Northridge earthquake! Similar magnitude earthquakes with different depths means that the felt shaking is different.
Damaging earthquake waves are largest near the hypocenter, or origin of the earthquake. Earthquake waves get smaller with increasing distance away from the hypocenter. The closer you are, the more you feel shaking!
Keypoints:
Learners will be able to:
Understand that depth from the hypocenter affects an earthquake's intensity.
Describe how depth impacts shaking intensity.
Relate how deeper earthquake means less intense shaking compared to shallower earthquakes.
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