[generally]

4 simulataneous quakes?? When does that ever occur naturally?

another one off by 19 sec.

[Steven W.]

aftershocks - hundreds by the time I looked at it.

[Publius]

After a major quake, they occur all the time. When the 6.7 Northridge quake occurred in January 1994, the earth shook constantly for hours afterward. Then came the 5.6 aftershock, followed by more shaking for days. You'd be surprised how little you care about minor shaking after a 6.7 quake.

[stars & stripes forever]

4 simulataneous quakes?? When does that ever occur naturally? another one off by 19 sec.

Probably the same quake, different monitors.