BC-APNewsAlert 09-28 0024
BC-APNewsAlert,0026
PARKFIELD, Calif. (AP) -- A strong earthquake has struck Central
California, according to the U.S. Geological Survey.
(Copyright 2004 by The Associated Press. All Rights Reserved.)
APTV 09-28-04 1126MDT
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BC-APNewsAlert 09-28 0024
BC-APNewsAlert,0026
PARKFIELD, Calif. (AP) -- A strong earthquake has struck Central
California, according to the U.S. Geological Survey.
(Copyright 2004 by The Associated Press. All Rights Reserved.)
APTV 09-28-04 1126MDT
Post more as it comes in, please.
aparently its right on the SA fault. there is an overdue prediction for a 6+ there.
5.8 is what I hear...
Looks like a 5er: http://www.data.scec.org/recenteqs.html Warning, this site is currently very busy.
Nevermind, SuPu's link is the same image and quickerer.
http://earthquake.usgs.gov/recenteqs...nc51147892.htm
Recent Earthquake Activity in the USA
Magnitude 5.9 - CENTRAL CALIFORNIA
2004 September 28 17:15:24 UTC
Preliminary Earthquake Report
California Integrated Seismic Net
USGS/ Caltech/ CGS/ UCB/ UCSD/ UNR
A moderate earthquake occurred at 17:15:24 (UTC) on Tuesday, September 28, 2004. The magnitude 5.9 event has been located in CENTRAL CALIFORNIA. The hypocentral depth was poorly constrained. (This is a computer-generated message -- this event has not yet been reviewed by a seismologist.)
Magnitude 5.9
Date-Time Tuesday, September 28, 2004 at 17:15:24 (UTC)
= Coordinated Universal Time
Tuesday, September 28, 2004 at 10:15:24 AM
= local time at epicenter
Location 35.775°N, 120.445°W
Depth 1.1 km (~0.7 mile) (poorly constrained)
Region CENTRAL CALIFORNIA
Distances 14 km (9 miles) NNW (336°) from Shandon, CA
14 km (9 miles) S (185°) from Parkfield, CA
23 km (14 miles) E (83°) from San Miguel, CA
27 km (17 miles) NE (52°) from Paso Robles, CA
217 km (135 miles) SE (143°) from San Jose City Hall, CA
Location Uncertainty horizontal +/- 0.8 km (0.5 miles); depth +/- 14.3 km (8.9 miles)
Parameters Nst=250, Nph=250, Dmin=8 km, Rmss=0.76 sec, Gp= 29°,
M-type=regional moment magnitude (Mw), Version=3
Source California Integrated Seismic Net
USGS/ Caltech/ CGS/ UCB/ UCSD/ UNR
Event ID nc51147892
I felt it at work in the Santa Cruz mountains. No problems here.
Funny, I didn't feel crap...but everyone else in the office did, WTF?
And, I thought you broke another bed.Quote:
Originally Posted by Punani
Felt it down here in Thousand Oaks, just west and north of L.A. It was a mere rumble down here. Just enough to make me pause as the blinds rattled a bit.
don't mind us, we're just seceding
Viva Republika de California. Arnold es mi Presidente!!!!Quote:
Originally Posted by tuffy109
Pfffft...Quote:
Originally Posted by Mcwop
Don't you remember the last time...
Earth quakes are a nice way to break-up boring meetings.
Were you TAKING a crap at the time? :DQuote:
Originally Posted by skier666
I used to live in WAAAAAAAY SoCal in the late 80's and we had a couple above 6. It was pretty wild. (I lived in El Centro....)
Was anyone in a swimming pool at the time? :p
Oh wow. I'm so sorry.Quote:
Originally Posted by 72Twenty
Tell me about it. That place sucked - and it was like 27 feet below sea level.Quote:
Originally Posted by CS
I'm a geology jong, anyone know if there is any relation between the Mt St Helens earthquake activity and this quake? Yeah, I realize they are hundreds of miles apart, just curious.
edit: El Centro is a serious hole.
Agreed, I also lived there at one point, but it was an extremely short stint, thankfully.Quote:
Originally Posted by cololi
It caused some minor damage, too. The city will henceforth be known as Nine Hundred Ninety-Nine Oaks... [cue rim shot]Quote:
Originally Posted by CS
Quote:
Originally Posted by CS
damn it. I just moved to Ventura, been here almost 3 weeks and still no quakes. totally unfair.
Only 5.9?
I've created larger tremors after eating a couple of Tommy's double cheeseburgers.
Yeah it is! I played Pop Warner Football there, though. That was my only good memory. That and skateboarding.Quote:
Originally Posted by cololi
My dad got transferred there for his job- he managed the Geothermal plant for Chevron. I remember we'd get little quakes in the middle of the night - just enough to trip the system and he'd have to go out there and reset everything.
Heh heh, I got kicked out of Catholic School there, though!!! :D
Hope all our Caliwogs are well and fine and watching their mts. grow
On looking at the earthquake map, there appear to have been something like 60 minor to 6.0 earthquakes near Parkfield, California (near Paso Robles). I lived in So Cal for 39 years and experienced a number of over 5.0s, but the one I'll NEVER forget is when I was in Visalia (not too far from this epicenter), my grandma was in the bathroom and the whole floor just turned liquid beneath me. I thought we were gonna die, get swallowed up by a crack or have the roof cave in on us. Even though the entire thing lasted over 30 seconds (long by earthquake standards) we were frozen in place, unable to move or walk. We found out later that the quake registered 5 something. On reading all this, I flashed back to that day and felt a panic rising inside me. Even though the Northridge earthquake was much stronger, I've never felt one scarier than the one I felt in Visalia. Nothing even fell or broke.
Someone asked whether Mt. St. Helens and the earthquake could be related. Absolutely. I'm sort of an amateur geologist, have been studying the stuff for decades....I've concluded that periods of high precipitation followed by great heat (that's September in the Central Valley for you!) seem to cause more earth movement. A volcano is fed by underground magma pools, when one erupts or emits steam or anything that causes it to give out materials inside, it creates an empty cavity, releasing pressure, allowing movement. The huge Mt. St. Helens eruption in 1980 was preceded by an extremely wet winter, and followed by a rash of many over 3.0 earthquakes.
Don't worry unduly, hardly anyone dies in an earthquake. Remember, without earthquakes there wouldn't be the Rockies, the Sierras, Cascades, etc.......
Its bizarre watching more and more earthquakes show up each time I refresh the screen on the first listed website.
Hope things turn out OK
Julie :(
I wanna see the ground give way.Quote:
Originally Posted by tuffy109
I wanna watch it all go down.
Mom please flush it all away.
Learn to swim.
Quote:
Originally Posted by skiingjulie
Um.... as a working geologist, I can aver that the two incidents have nothing to do with each other. The seismic forces at work for this recent 5.9 quake has nothing to do with the volcanic seismic forces at Mt. St. Helens. They're too different mechanisms created by two entirely different tectonic situations.
In addition, the theory that earthquakes are more frequent after periods of high precipitation is shakey (pun intended) at best and ONLY relates to seismic activity from a tectonic source, not from volcanism. While there is some physical and theorhetical evidence to support this line of thought, the general consensous amoung geologists is that the increased likelyhood is very slight at best. There is no evidence that I know of that indicates that volcanic activity or related seismic activity is influenced to a measureable or percievable amount due to climactic fluxuations. It's not my forte as a geologist, so there may be some recent studies in the last few years that say differently, but I highly doubt it. Are there any?
Damn, now I have to go look for my sources of information. I can't remember if it was in Scientific America or...... Anyway, I thought earthquake prediction was a VERY inexact science. I remember all the debate in the 70's: do frequent small earthquakes lead to bigger, subsequent ones or do they relieve pressure? I've had a number of colleagues look at data on rain, volcanic activity and earthquakes. There seems to be a connection, but we may never be able to actually quantify it.
I wasn't trying to step on anyone's toes or question your expertise, just throwing out some fodder for thought. What are some correlations with earthquakes and anything else??????
Say what you want, I never jumped too high while living in SoCal (LOL)
Earthquakes correlate to the ground shaking and, if it's a big one, subsequent interviews conducted by television reporters with the biggest, dumbest, shirtless oafs or house-fraus (usually with thier hair up in curlers even if it's 3:00 in the afternoon) in thier dundies that they can find! ;)Quote:
Originally Posted by skiingjulie
No toes were stepped on. I just wanted to set the record straight as I saw it! :)
Our understanding of tectonic earthquakes (the ones resulting from shifts in the plates, etc) is terrible. It's a part of the science that's still in it's infantile stages. We know general areas where tectonic earthquakes occur, and that's about it. Forget about trying to predict where, when or to what intensity. The only true correlations that earthquakes have is that they almost all occur adjacent to plate boundaries or in areas of volcanic activity. There's a few other places that they occur, but they're fairly rare.
Also, someone mentioned that they're expecting "The Big One" sometime on the San Andreas Fault. This is only sort of true.
The pseudo-prediction says that "The Big One" will likely happen somewhere near Cajon Pass or San Bernardino, which is many hundreds of miles away from where this latest quake occured. In addition, the "Big One" scenario is based on a slip-rate for the San Andreas that came about from a paper written by a geologist named Kerry Sieh back in the early '80s on offset peats in a prehistoric bog north of Los Angeles. While it's a well written paper, many geologists have been questioning it's relativity to the rest of the San Andreas Fault. In predicting the location of "The Big One," a whole lot of other data is used, as well as a whole lot of assumptions. As such, most geologists (especially ones studying the Los Angeles Area) refute the credibility of the "Big One."
I, too, don't think the idea of the "Big One" holds much water. I'm not saying that I don't think it will happen, just that we don't have any idea if it will or not, or even where it will occur if it should occur. I certainly wouldn't avoid areas like Los Angeles or San Francisco because of earthquakes. My thought is that no matter where you live, there's always a threat of some sort of natural disaster.
Quote:
Originally Posted by Ubersheist
GRRRRRRRRRRRRRR!!! You're starting to PISS ME OFF!!!!
Yep, Ubersheist (how do you umlaut?). Living for years in the Inland Empire, we would always observe a moment of silence as we passed over Cajon Pass (San Andreas/San Jacinto Faults). I'm familiar with the studies of which you speak and agree with most everything you say (especially correlations with dumbshit reporters, eyewitnesses, etc. ;)
I'm getting all tingly knowing someone else interested in geology is on the boards. People usually stare at me dumbly and ask, "what's so interesting about a bunch of rocks?...." When I tell them I'm especially interested in Meteorology, they nod in a "She's crazy and weird but I'll humor her" sort of way.
Anyway, I enjoyed the discourse.
Hope things settle down in Cali so people have a chance to collect themselves and let everyone know how they're doing. Our attempts at "scientificizing" :eek: natural catastrophes is by no means an attempt to downplay our sympathies and concern.
Take care all
5.8s are pretty fun nice lttle jolt I've felt 7s they were pretty far away but long kinda freaked me out cause the '64 quake was a long about 7 and then it jolted like hell... Earthquakes are fun
Yeah, i bet the poor fuck that didn't quite clear this gap thought it was fun...Quote:
Originally Posted by ak_powder_monkey
http://wrgis.wr.usgs.gov/dds/dds-29/screens/016sr.jpeg
http://www.metroactive.com/urbanview...uide1-0237.jpg
I still remember dropping my jaw when I saw the home video footie of that lucky mother...
That was just because NorCal engineers are morons. ;)
Gee...let's build a very large bridge on top of wooden piling that will eventually rot. We are so SMRT!!!!
And don't get me started on the Nimitz freeway. That took over a decade and a half to rebuild. LA got up and running months after the Northridge quake.
The 5/14 interchange didn't fare so well either, so naturally I'm just joking.
As far as offering symapathies and stuff, it's appreciated. However, I'd say most earthquakes in the US are non-events. Sure the house shakes and you run into a doorjamb. Maybe a few glasses break too. But the devastation is generally nothing in comparison to the havoc hurricanes and tornados wreak on the rest of the country. After all, there's no such thing as a small hurricane.
Small earthquakes however comprise most of the events out here. Every couple of decades you have a larger one hit though, and it will cause some damage. But it's not like entire neighborhoods are leveled and whole cities are evacuated. In the last 28 years there have only really been 3 earthquakes of note damage wise: Whittier Narrows (5.9), Northridge (6.7), and Loma Prieta (6.9). This most recent quake occurred in a relatively unpopulated area. The three I mentioned above were all in major metropolitain areas. Now compare this to the number of hurricanes that hit Florida this year alone. I'll take earthquakes thank you very much.
Things don't start getting interesting until you hit around 6 and up. I've been in a couple of 5s and they weren't a big deal. In fact you can sleep through most of the smaller ones. Whittier scared the shit out of me, but it was also my first earthquake. I was on the opposite end of the state for the Northridge and Loma Prieta quakes luckily.
What people also forget to mention is that one's proximity to the quake is very important. I once met a seismology professor at CalTech and he explained that a "Big One" (say an 8.0 on the San Andreas) really wouldn't be that big of a deal. By the time it reached say Pasadena, it would feel similar to how the Whittier quake felt in the same city. Depending on who you talked to about the Northridge quake, it was either horrible or not that bad. The answer would always correlate with distance from the epicenter.
There is one more thing to add, there are different types of quakes also. I don't know the technical terms, but some are very jarring while others have more of a rolling motion. The rolling ones aren't so bad. They kinda shake you back and forth in a wavy motion. It's the jarring ones that fuck with your head. They're much more violent It's similar to being on a flight with really bad turbulence. They're really quick shocks that make you feel like your going to fly straight up out of your seat and hit your head.
It's not just the distance from the epicenter it's also the type of ground you're standing on, the depth of the shock and the wavelength the shock has generated.
Don't forget the San Fernando earthquake of '71 (a 6.6). It really messed a lot of things up (near LA). It's where the Valley girls used to jive.
P-waves cause alternating compressions and expansions (like smashing into the side of a tectonic plate with a really big truck). S-waves are shear waves that oscillate at right angles to their direction of motion and supposedly cannot travel well through liquids. P waves travel faster than Ss. Then there are surface (or L)waves which travell along the top of the crust that toss things in a way similar to what the ocean does to boats, etc. They also have a side to side component that causes the most damage to buildings and foundations.
This is a dangerous misconceptions. Door jams tend to be attached to doors that get violent in big quakes. A hallway is a much safer place.Quote:
Originally Posted by Arty50
This is only half true. Yes, it does matter how far away you are. However, a huge often overlooked factor is the geology that you're on at the time of the quake. If you're on top of a thick sequence of unconsolidated alluvial material, the ground acts sort of like a spring, making the shaking far more intense then if you were built on solid bedrock, like granite or sandstone. This is in part why some houses (probably built on man-made fill) in the Northridge quake crumbled, while the house next to it (with it's foundations firmly placed on natural soils or solid rock) withstood the shaking.Quote:
I once met a seismology professor at CalTech and he explained that a "Big One" (say an 8.0 on the San Andreas) really wouldn't be that big of a deal. By the time it reached say Pasadena, it would feel similar to how the Whittier quake felt in the same city. Depending on who you talked to about the Northridge quake, it was either horrible or not that bad. The answer would always correlate with distance from the epicenter.
Also, if you did get an 8.0 in the Inland Empire, you'd get the shit scared out of you for sure in Pasadena. No question. That would be about the same distance from the Northridge Quake's epicenter as I was during that quake's shaking. It scared the daylights out of me. Mind you, the condo I was living in was probably built on fill...
Actually, there's two types of earthquakes - tectonic (which we're talking about here) and ones related to volcanic (obviously not what we're talking about here). Niether one has a "rolling" effect greater then the other.Quote:
There is one more thing to add, there are different types of quakes also. I don't know the technical terms, but some are very jarring while others have more of a rolling motion. The rolling ones aren't so bad. They kinda shake you back and forth in a wavy motion. It's the jarring ones that fuck with your head. They're much more violent It's similar to being on a flight with really bad turbulence. They're really quick shocks that make you feel like your going to fly straight up out of your seat and hit your head.
The "rolling" effect has to do with the fact that there's three sorts of seismic waves eminating from any earthquake's epicenter. First you get Primary Waves (or P-waves). These physically travel faster then the other types of waves and shake the ground back and forth without much up and down movement. The second fastest type of seismic wave (and the second to hit you) is uncreatively called Secondary Waves (or S-waves). These give you the horizontal shaking or "rolling" feeling. The third type is a wave whose name I can't remember - it's named after some dead scientist's name. They shake side to side. They're generally not as strong as the two other seismic wave types.
If you feel a rolling sensation, you're probably a good distance away from the epicenter. P-waves dissapate faster then S-waves because P-waves can travel through the liquid mantle of the planet. S-waves must remain in the crust, as they get reflected back as soon as they hit the crust/mantle contact and maintain more of thier energy over a distance. As such, 30 miles or so away from an epicenter will have more of a "rolling" feeling then a back and forth or side to side feeling. With that sort of distance, the earthquake has had enough area to disipate over. Therefore, the "rolling" wouldn't seem quite as bad as your "jarring" quake.
Hope that clears stuff up!
Hey, don't leave us in the PNW out. The Nisqually quake on Feb. 28, 2001 was pretty good (6.8). It caused a fair amount of damage in Seattle and elsewhere.Quote:
Originally Posted by Arty50
Fault types are also a factor in the type of earthquake. The Northridge earthquake was on a reverse or normal fault, I can remember exactly but the motion is similar. The San Andreas and most off-shoot faults are strike-slip.
Reverse and Normal faults have an up and down slip characteristic, think mountain building. Strike/Slip slide next to each other, the reason LA & SF will be suburbs of each other one day.
The Northridge quake was on a previously unknown Reverse fault. In my opinion the reason there was more widespread and severe damage with this quake was that most of the earthquake engineering in So Cal is designed for strike/slip motion.
I was in the 6.6 Sylmar quake of 1971, living in Northridge ironicaly enough. I was 9 years old. I can recount every second (61 of them) as if it happened yesterday. Our house slipped forward 2 inches, the driveway buckled, the chimney fell, all brick fences in the neighbor collapsed, the curb seperated from the street 2 inches. We had no power for 2-3 days and no water for 8 days. People often say a 6.6 isn't that big but from my experience it was huge and was the impetus for me to get my degree in Geology.
A thought to ponder for the other geo nerds. Is there a link between the increased activity in the Long Valley Caldera(Mammoth area) a couple of weeks a go and Mt St. Helens reawakening? Huge magma river?
The fault type has no bearing on an "earthquake type." Remember, there are essentially only two types of earthquakes:Quote:
Originally Posted by gageyk
- Tectonic, most commonly due to movement along any type of fault
- Volcanic - which is related to the movement of magma underneath the ground.
The only discernable differences in the seismic waves (earthquakes) produced by different fault types only is apparent in data from sensitive measuring equiptment (seismographs and other equiptment). There's no discernable damages, experiences or differences between a 6.0 from a thrust fault or a 6.0 from a strike/slip fault.
This may be true about 10 million years from now or more. Here's an interesting thought:Quote:
Reverse and Normal faults have an up and down slip characteristic, think mountain building. Strike/Slip slide next to each other, the reason LA & SF will be suburbs of each other one day.
There's a strong contingency of geologists that think the plate boundary between the Pacific and North American Plates will jump from the current San Andreas Fault, and create a new fault from the Salton Sea area up to the Owens Valley Fault area, and then northwards, possibly up to Reno, and cutting back somewhere that's undefined and unknown at this time. With this scenario, Mammoth may become a suburb of Reno in a few million years. However, the mountain will surely blow up by then, so the point will be moot!
The Northridge quake was located on a "blind thrust fault." These are relatively newly discovered phenomena that has only been recognized in the last 10 to 15 years. Essentially, it's an active fault that's been buried with sediment, and therefore has no evidence of it's existance at the surface. They're extremely hard to find. You are right, though... No one knew about the blind thrust fault that produced the Northridge Quake.Quote:
The Northridge quake was on a previously unknown Reverse fault. In my opinion the reason there was more widespread and severe damage with this quake was that most of the earthquake engineering in So Cal is designed for strike/slip motion.
Most of the damage occurred on buildings that were either relatively old and were built when certain modern building practices were not used, or on newer buildings that used poor building practices (i.e. the contractors got away with putting in substandard rebar in the footings, interiors were not built to code, etc.)
A 6.6 is PLENTY big. I'll bet your draws were brown after that episode.Quote:
I was in the 6.6 Sylmar quake of 1971, living in Northridge ironicaly enough. I was 9 years old. I can recount every second (61 of them) as if it happened yesterday. Our house slipped forward 2 inches, the driveway buckled, the chimney fell, all brick fences in the neighbor collapsed, the curb seperated from the street 2 inches. We had no power for 2-3 days and no water for 8 days. People often say a 6.6 isn't that big but from my experience it was huge and was the impetus for me to get my degree in Geology.
Huge magma river? Where'd that come from? Convection cells?Quote:
A thought to ponder for the other geo nerds. Is there a link between the increased activity in the Long Valley Caldera(Mammoth area) a couple of weeks a go and Mt St. Helens reawakening? Huge magma river?
The volcanic activity at Mammoth is essentially entirely unrelated to the volcanism at Mt. St. Helens. If you have been recently working in geology, you should know this. Remember volcanism as it relates to subduction zones versus hot spots? Mammoth is on top of a hot spot of sorts. Mt. St. Helens is a result of the small Juan De Fuca Plate (a small relic tectonic plate of the former Farallon Plate wedged in between the Pacific Plate and the North American Plate) being subducted under the North American Plate. The two have extremely little to do with each other.
Man - I do like rocks! My boss would be PISSED to see me writing all this crap on the board instead of making him money!
We just got another one.
A bit softer than yesterdays, but longer.