W.L. Ellsworth J. C. Tinsley R. F. Yerkes 1983 <div id="15568209" class="article-section-wrapper js-article-section js-content-section " data-section-parent-id="0"><p>A reverse-right-oblique surface rupture, associated with a M_L<span>&nbsp;</span>2.5 earthquake, formed in a diatomite quarry near Lompoc, California, in the northwesternmost Transverse Ranges on April 7, 1981. The 575-m-long narrow zone of ruptures formed in clay interbeds in diatomite and diatomaceous shale of the Neogene Monterey Formation. The ruptures parallel bedding, dip 39°–59°S, and trend about N84°E on the north limb of an open symmetrical syncline. Maximum net slip was 25 cm; maximum reverse dip slip was 23 cm, maximum right-lateral strike slip was about 9 cm, and average net slip was about 12 cm. The seismic moment of the earthquake is estimated at 1 to 2 × 10¹⁸<span>&nbsp;</span>dyne/cm and the static stress drop at about 3 bar. The removal of an average of about 44 m of diatomite resulted in an average load reduction of about 5 bar, which decreased the normal stress by about 3.5 bar and increased the shear stress on the tilted bedding plane by about 2 bar. The April 7,1981, event was a very shallow bedding-plane rupture, apparently triggered by crustal unloading.</p></div> application/pdf 10.1130/0091-7613(1983)11<287:TRFAED>2.0.CO;2 en Geological Society of America Triggered reverse fault and earthquake due to crustal unloading, northwest Transverse Ranges, California article