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USGS CMG InfoBank: Alignment Array Surveys

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Comment: 19:49 - 21:02 (01:13)
Source: Annenberg/CPB Resources - Earth Revealed - 9. Earthquakes
Keywords: "alignment array", "fault slip", "Robert O. Burford", "San Andreas Fault", "slip rate", "creep meter", fault, Parkfield

Our transcription: To derive the same kinds of information as provided by a creep meter but over a wider area, geophysicists use what's known as an alignment array.
This involves setting up markers, then conducting surveys across the San Andreas Fault to determine the local slip rate, the width of the slip zones, and patterns of deformation near the fault trace.
The alignment array surveys are also useful in helping scientists determine the best places to install creep meters.
The alignment array is similar to the creep meter in that it's measuring fault slip right at the surface trace.
However, the creep meter is a continuous monitoring device for the center of that slip area; whereas, the alignment array goes much farther away from the fault to be sure that we're not missing some important slip on auxiliary fractures out to the side.
In the alignment array, of course, we only get data when we make surveys; whereas, the creep meter can be run continuously, and we can look at that every day to see how much the center of this zone has actually moved.

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