Virtual Lab Tour - Shallow Crustal Faults

Shallow Crustal Faults

The final area which produces earthquakes are the shallow crustal faults. These are shallow faults that occur at the very top of the earth's crust (less than a kilometer deep) right up near the surface. These kinds of earthquakes are potentially the most damaging to the uban areas of the Puget Sound because the movement occurs right at the surface underneath areas of major population. This means that the shock waves do not get dampened as they travel through the rock. Also, due to the shallowness of the fault, ruptures can occur right at the surface, causing massive damage.

These types of earthquakes are potentially the biggest threat to the Seattle area. The biggest and potentially most dangerous fault is the Seattle fault, which runs right underneath Seattle where the Kingdome used to be and west underneath the water out to Bainbridge Island and east out to Issaquah. The last time this fault ruptured was about 1100 years ago causing great transformations in the landscape of the area.

We can see in this picture taken through a technique called Lidar, evidence of the uplift caused by the quake that happened 1100 hundred years ago. We can also see the fault scarp created by the sliding of rocks past each other.

Here we can see what the uplift actually looks like today. This is a place called Restoration point located on Bainbridge island, right across the water from Seattle (in the background). The flat area between the trees and the water is the area uplifted by the last earthquake.

To learn more about shallow crustal faults, click here.

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