I work at salton city, desert shores and salton sea beach everyday for the state. Something one might take into consideration is that there is some "dormant" volcanoes hanging around on the the northeast end of salton sea. They seem pretty active as we have plenty of geothermally active geysers and mud bogs in the same area. Could the smell, (which only stunk for one day, I know cause I was there), be a release of volcanic gases as a result of the constant quakes and fissures opening up around the valley?

Volcano under the Salton Sea. If a serious eruption happens the effect would be magnified as the hot gasses and magma pour out cold water would pour in, this would multiply the potential explosive power of the eruption.
Volcanic Eruption possible near Salton Sea
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I'll second the idea of the smell being connected to volcanic out gassing. The area has the distinction of being one of the few where an 'oceanic' spreading center appears on land (like the African Rift Valley & Iceland). The region lies directly on top of the East Pacific Rise. Some of the earthquakes swarms that strike the region (like the one that struck the week before the smell) are known to be caused by magma injection (basalt) from the spreading center (dike emplacement). The fish die offs happen occasionally (they've happened before many times) but never have they been accompanied by a smell like this that affected us here in Los Angeles.