These are due to:
Marines firing 155 mm howitzers at Pendleton, again.
2(6.2%)
Military aircraft breaking the sound barrier somewhere around here
3(9.4%)
Alien spacecraft breaking the sound barrier
6(18.8%)
SURFACE TO AIR MISSILES
5(15.6%)
Tank farms in Long Beach blowing up
2(6.2%)
Thunder in the Santiago/Saddleback mountains
1(3.1%)
Hallucination
1(3.1%)
Earthquakes
2(6.2%)
Atmospheric conditions amplifying Disneyland fireworks
3(9.4%)
Naval battle off the coast
2(6.2%)
Volcanic activity
0(0.0%)
Other (please comment)
5(15.6%)