John Gaquin wrote:
"Frogwatch" wrote in message

It clearly felt like two waves like going over a large speed bump
slowly. The waves were each about a second long and separated by less
than a second. Later ones were much shorter in duration and felt like
simple jolts and much less intensity. They came about 5 seconds after
the first and then a couple more maybe 10-20 seconds later. No objects
in the house shook or rattled.

I like to hear first-person accounts rather than analysis from film or paper
record, which is what we did years ago. I suppose they feed it right into a
computer now.

Its interesting that the quake measured 6.0 on the Richter scale, but at
your location only what sounds like about a II on the Mercalli, which
quantifies local intensity. Off the cuff, I'd guess that indicates a
rather deep focus quake. The first two rapid jolts you felt were probably
the primary waves direct from the epicenter, while the ones 5 seconds later
were likely those same primary waves reflected or refracted off parts of the
earth's inner structure. The movement you felt at 10-20 seconds could have
been the longer-period surface waves. In large earthquakes, particularly
those near the surface, these are the waves that tend to wrench buildings
apart and open wide fissures in the ground. But in small, deep quakes, its
just interesting to observe. Thanks for the description.

The 10-20 second wave cycles could also have been aftershock. But you
may also be correct in that the wave cycles may have been caused by the
Ms (surface wave). I'd agree that the first shake he felt was probably
the P-wave.

basskisser wrote:
John Gaquin wrote:
"Frogwatch" wrote in message

It clearly felt like two waves like going over a large speed bump
slowly. The waves were each about a second long and separated by less
than a second. Later ones were much shorter in duration and felt like
simple jolts and much less intensity. They came about 5 seconds after
the first and then a couple more maybe 10-20 seconds later. No objects
in the house shook or rattled.

I like to hear first-person accounts rather than analysis from film or paper
record, which is what we did years ago. I suppose they feed it right into a
computer now.

Its interesting that the quake measured 6.0 on the Richter scale, but at
your location only what sounds like about a II on the Mercalli, which
quantifies local intensity. Off the cuff, I'd guess that indicates a
rather deep focus quake. The first two rapid jolts you felt were probably
the primary waves direct from the epicenter, while the ones 5 seconds later
were likely those same primary waves reflected or refracted off parts of the
earth's inner structure. The movement you felt at 10-20 seconds could have
been the longer-period surface waves. In large earthquakes, particularly
those near the surface, these are the waves that tend to wrench buildings
apart and open wide fissures in the ground. But in small, deep quakes, its
just interesting to observe. Thanks for the description.

The 10-20 second wave cycles could also have been aftershock. But you
may also be correct in that the wave cycles may have been caused by the
Ms (surface wave). I'd agree that the first shake he felt was probably
the P-wave.

Cool. We have no experience with earthquakes here so it was a really
novel thing.