Stress-drops for small to moderately sized earthquakes in Southern California are found to vary systematically with source-depth and location (tectonic environment). We determine high-quality fault-plane solutions, plus depth and source duration, for 17 significant (M>3.9) aftershocks associated with the June 28, 1992 Big Bear sequence, including the more recent April 4, 1994 19:04 GMT Mw 4.6 Lake Arrowhead aftershock, and a Mw 4.2 Banning Pass event which occurred on May 31, 1993 at 08:55 GMT. Given source durations and moments obtained from long-period source estimations, and assuming a circular fault model, we estimate stress-drop for each event. Big Bear aftershocks are moderate to high (>100 bars) stress-drop. Events deeper than 12 km are generally high stress-drop (>100 bars), while shallower events exhibit moderate to high stress-drops. These results are compared with a similar analysis of Landers aftershocks in the Mojave block. For the Big Bear region, stress drops appear to correlate with depth, with the deepest events yielding the highest stress-drops. In general, events in this region yield higher stress-drops than events occurring in the Mojave block and those associated with the Landers and Joshua Tree sequences. Comparisons of ML to Mo are consistent with the stress-drop results: deep, high stress-drop events show elevated ML to Mo ratios. ¿ American Geophysical Union 1996