OBLIQUE SLIP
OBLIQUE SLIPMaterials:
Procedure:
After reading these directions, go to the animations page. If necessary, scroll down to the first animation, example 1. You may need to use the Reload button on your browser to restart the animation. Try and carefully watch the slip depicted in the animation. The viewing angle can make this tricky -- keep in mind that the two sides of a fault always stay in contact with each other, so there will not be a gap between the animated blocks at any time.
What sense of lateral slip occurs? What sense of dip slip? Remember that oblique-slip faults are named simply by a combination of the sense of lateral slip followed by the sense of dip slip. Decide on a name for this oblique-slip fault.
Once you have done this, click on the image to
go to the appropriate example on the answer page.
Then use the link provided to go back to the next example on
the animations page, until you have finished with all
three examples.
Would you consider all these examples to be "obvious"
oblique-slip faults -- that is, were the components of dip slip and
lateral slip roughly equal?
Additional Notes:
The perspective may have caused you problems. Though this particular problem is not encountered in the real world (since you can generally view a fault from several different angles), oblique slip faults can be confusing, even to geologists. Of particular note is the Raymond fault in the Los Angeles area. The fault has created an obvious scarp which stretches for many miles through Pasadena, San Marino, South Pasadena and other nearby towns. For years it was assumed that the elevation change of 30 meters along this scarp meant the Raymond fault was a reverse fault, probably with some small component of left-lateral slip. The Pasadena earthquake of 1988 changed that notion. That earthquake, which occurred along the Raymond fault, was predominantly left-lateral with only a small reverse slip component. Upon closer geological study, it was found that the 30 meters of vertical offset that created the scarp (through the action of many surface ruptures repeated over thousands of years) had been accompanied by 400 meters of left-lateral offset, meaning the lateral-to-dip-slip ratio of this fault is roughly 15 to 1! This agrees very well with the ratio deduced from the Pasadena earthquake.
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