And what country can preserve its liberties if their rulers are not warned from time to time that their people preserve the spirit of resistance? Let them take arms. The remedy is to set them right as to facts, pardon and pacify them. What signify a few lives lost in a century or two? The tree of liberty must be refreshed from time to time with the blood of patriots and tyrants.
Friday, June 27, 2025
Felt that one. Unlike the usual gentle roll, that one was a sharp slam., as if something hit the house.
I was born in SoCal in the late 50s and have lived thru many earthquakes in SoCal and in SF thru the years. If one is not above 6 in mag it really does not get felt and if not above 6.4 there is not damage. 6.5 and above is where people start getting hurt.
Being upstairs a lot, I regularly experience anything above about a 3 anywhere south of Santa Barbara. Nearby trains don't make the dangling light sway. Earthquakes do.
The initial "slap" is the P-wave - P for pressure. It travels faster than the S-waves - S for shear. For a more distant quake, you can estimate the distance to the epicenter by the delay from the first P-wave until you feel the S-waves.
That explains why the earthquakes I've felt in my life have been completely different in amplitude and frequency. The first one I felt must have been the "P" wave and I heard a faint rumble before it hit. It was sharp fast and very scary. The other earthquake I was aware of was like riding waves on the ocean.
Distance make a difference. Driving in Orange County and though a tire blew out. Checked, nothing wrong. Got to work and found out it was an earthquake. Short and sharp. It was close, just off the coast but weak - 4ish.
Geology also makes a difference. Mexico City Center was farther from the epicenter, but due to the underlying geology (sand), was effected more than cities that were closer (rock).
It is projected that a major quake that would radiate through Southern California (30 sec +/-) could shake the LA Basin for up to 3 minutes...... Video is from the 2014 California ShakeOut Scenario - https://www.youtube.com/watch?v=nvltp9Nf5T4
Had a paltry 5.0 hereabouts a coupla years back, which usually would be a mouse phart, but it was 1/4 away, a really shook the crap out of the place when you're nearly on top of it.
The little ones used to be fun for surfing the floor, until you have a really big one that starts out exactly the same until it gets bigger and Bigger and BIGGER.
So now even the little ones can elicit a need for fresh underpants.
I live in New Zealand. We are called the shakey isles for good reason. Last biggish one was a 7.5 something about 40 miles away. It lasted ages and I got out of bed to enjoy it from my deck. Quite the experience and saw the earthquake lights that were thought to be imaginary. A big one (8 plus) on our local fault is technically overdue, there are horizontal displacements of 40 feet from earlier ones and a biggie in 1855 lifted the local hills 25 feet. Its quite sobering to be living on an active fault line. My dog goes nuts when we have one.
When you say "not the usual gentle roll"...how often do you get these CW? I remember experiencing a 5.1 and it was a pretty sharp. Steve_in_Ottawa
ReplyDeleteRarely
DeleteI was born in SoCal in the late 50s and have lived thru many earthquakes in SoCal and in SF thru the years. If one is not above 6 in mag it really does not get felt and if not above 6.4 there is not damage. 6.5 and above is where people start getting hurt.
ReplyDeleteBeing upstairs a lot, I regularly experience anything above about a 3 anywhere south of Santa Barbara. Nearby trains don't make the dangling light sway. Earthquakes do.
DeleteThe initial "slap" is the P-wave - P for pressure. It travels faster than the S-waves - S for shear. For a more distant quake, you can estimate the distance to the epicenter by the delay from the first P-wave until you feel the S-waves.
ReplyDeleteThat explains why the earthquakes I've felt in my life have been completely different in amplitude and frequency. The first one I felt must have been the "P" wave and I heard a faint rumble before it hit. It was sharp fast and very scary. The other earthquake I was aware of was like riding waves on the ocean.
DeleteDistance make a difference. Driving in Orange County and though a tire blew out. Checked, nothing wrong. Got to work and found out it was an earthquake. Short and sharp. It was close, just off the coast but weak - 4ish.
ReplyDeleteGeology also makes a difference. Mexico City Center was farther from the epicenter, but due to the underlying geology (sand), was effected more than cities that were closer (rock).
It is projected that a major quake that would radiate through Southern California (30 sec +/-) could shake the LA Basin for up to 3 minutes...... Video is from the 2014 California ShakeOut Scenario - https://www.youtube.com/watch?v=nvltp9Nf5T4
Yeah.
ReplyDeleteHad a paltry 5.0 hereabouts a coupla years back, which usually would be a mouse phart, but it was 1/4 away, a really shook the crap out of the place when you're nearly on top of it.
The little ones used to be fun for surfing the floor, until you have a really big one that starts out exactly the same until it gets bigger and Bigger and BIGGER.
So now even the little ones can elicit a need for fresh underpants.
Hope old Shasta does not open up on you Boss!
ReplyDeleteI live in New Zealand. We are called the shakey isles for good reason. Last biggish one was a 7.5 something about 40 miles away. It lasted ages and I got out of bed to enjoy it from my deck. Quite the experience and saw the earthquake lights that were thought to be imaginary. A big one (8 plus) on our local fault is technically overdue, there are horizontal displacements of 40 feet from earlier ones and a biggie in 1855 lifted the local hills 25 feet. Its quite sobering to be living on an active fault line. My dog goes nuts when we have one.
ReplyDelete