Mapping Micro Slip on a Fault

The Long Beach Array sits atop a segment of the Newport-Inglewood Fault Zone (NIFZ). The 1933 Long Beach earthquake, which caused wide-spread damage in the Los Angeles region occured on this fault just to the SE of the array. Many of the oilfields in the Los Angeles Basin are along the NIFZ.

The geometry and density of the array makes it possible to estimate the activity on the NIFZ. To do this, we have made a movie of the apparent micro-slip on the fault. To make a frame in the movie, the data from the array are back-projected onto the plane of the NIFZ. The result shows a sense of the activity on the fault. Note that these are very small motions.
                Click image to run movie
A cartoon showing the approximate location of the NIFZ and the Long Beach array (on the top of the cube). One fram of the movie is shown projected onto the NIFZ. The white star is one of the events located by the array. The full movies (600 s) is in the right panel. The movie of micro-slip on the NIFZ. The movie shows that there is a lot of micro-activity on the fault.