Magnitude 4.9 earthquake in Utah.
Northern Utah on the UT-WY border. Felt reports coming into the USGS are currently from as far south as American Fork, UT and as far west as the Great Salt Lake. This isn't a major one, and no idea of any damage yet. It's of interest because it's an intraplate earthquake, despite it being not-unexpected because of its location in the far-east end of the Basin and Range Province.
A group called Earthscope was hopefully able to pick up some good data from this quake. I mention them specifically because they held a small conference on campus earlier this week. Regrettably, I was only able to attend one session - it was absolutely fascinating! The discussions on seismology and tectonic work, as well as their goal of setting up a high-res seismic array in North America is a fascinating listen. I can't even imagine what such a network will do for tomography underneath the North American Plate.
In other news, was on a field trip last weekend and am leaving for another tomorrow at noon. St. Francois Mountains or bust!
Showing posts with label earthquake. Show all posts
Showing posts with label earthquake. Show all posts
Thursday, April 15, 2010
Thursday, March 11, 2010
More Big Quakes in Chile
These are probably aftershocks, but I got these e-mails from the USGS about an hour ago:
Magnitude 7.2, Libertador O'Higgins, Chile 3/11/10 14:39:48 UTC
[This has since been revised down to magnitude 6.9.]
Magnitude 6.9, Libertador O'Higgins, Chile 3/11/10 14:55:30 UTC
[This has since been revised down to magnitude 6.7.]
Magnitude 6.0, Libertador O'Higgins, Chile 3/11/10 15:06:03 UTC
Aftershocks may continue for years after a quake in some cases, but these are strong. I couldn't say for sure whether these are indeed aftershocks or this is a new section of the fault breaking. Not my area of expertise, but I'll post a link if I can find anything on that after my class this morning.
What I'm finding strange about these earthquakes (aside from the third, which doesn't have first motion data and hence no focal mechanisms/moment tensors yet) is that they are not compressional, as you'd expect from the proximity to the subduction zone off of the Andes mountains. They are extensional. I'll have to look into this more after class as well.
As a note, revisions to magnitude are common as more seismograph stations worldwide pick up tremors from an event. The more data we have, the better we can characterize the motions and strength of the event.
Magnitude 7.2, Libertador O'Higgins, Chile 3/11/10 14:39:48 UTC
[This has since been revised down to magnitude 6.9.]
Magnitude 6.9, Libertador O'Higgins, Chile 3/11/10 14:55:30 UTC
[This has since been revised down to magnitude 6.7.]
Magnitude 6.0, Libertador O'Higgins, Chile 3/11/10 15:06:03 UTC
Aftershocks may continue for years after a quake in some cases, but these are strong. I couldn't say for sure whether these are indeed aftershocks or this is a new section of the fault breaking. Not my area of expertise, but I'll post a link if I can find anything on that after my class this morning.
What I'm finding strange about these earthquakes (aside from the third, which doesn't have first motion data and hence no focal mechanisms/moment tensors yet) is that they are not compressional, as you'd expect from the proximity to the subduction zone off of the Andes mountains. They are extensional. I'll have to look into this more after class as well.
As a note, revisions to magnitude are common as more seismograph stations worldwide pick up tremors from an event. The more data we have, the better we can characterize the motions and strength of the event.
Monday, March 8, 2010
More Chilean Earthquake Stuff and Mars
In other news, Concepcion, Chile is now sitting ten feet further west than it did previous to the magnitude 8.8 earthquake.
Only about 3.1 meters displacement, you say? For one event, that is pretty damn significant. That and in the grand scheme of things, there's only a smidgen of crustal shortening and subduction going on there. Amazing to think about how much ocean crust once did exist there before the subduction zone developed. But alas, as the ridge is still actively spreading, the crust must go somewhere!
Something about that whole conservation of mass thing . . .
Then there's this article about Mars. Cool. One of the great questions about Mars is centered around what controlled the erosional and sedimentary features on the planet's surface and what happened to it.
Mars' surface yields some spotty paleomagnetic evidence of possible early plate tectonics (I like to think so, at least. However, it's not universally accepted and other models exist), but it's plainly evident that whatever the tectonic style of the planet, it shut down while Earth was still in the Precambrian Eon (I guess it's considered a "Supereon"?). Mars is just too small to maintain plate tectonics/convection cycles like those of Earth - the heat gradient from core to surface is too steep. I could talk all day about what I think about the formation of the giant shield volcanoes and Tharsis, but that's not what the article's about. Well, it could tie into Tharsis. But it's not directly about it.
Later on, sedimentary features developed - most strikingly, the canyons larger than any found on Earth. Whatever fluids and erosional processes that once controlled this are mostly gone now. It's now being postulated in this article that some of the channel features were carved out by lava.
I can buy this - camped in Snow Canyon State Park in Utah a couple of years ago. It admittedly started as a canyon carved by fluvial (waterflow-driven) processes, but was located proximal to a basaltic magma source as young as 20,000 years old. Eruptions there changed the course of the river - partly by building up topography in some places and carving it out in others. Redirection of waterways carved new, deeper canyons and remnants of older lava flows can be seen near the top of the present day canyon. This is a phenomenon called "inverted topography," where younger rock sits lower than older rock. This is only one way to form inverted topography, but that could be a blog post in and of itself, so maybe I'll save that for another post.
Only about 3.1 meters displacement, you say? For one event, that is pretty damn significant. That and in the grand scheme of things, there's only a smidgen of crustal shortening and subduction going on there. Amazing to think about how much ocean crust once did exist there before the subduction zone developed. But alas, as the ridge is still actively spreading, the crust must go somewhere!
Something about that whole conservation of mass thing . . .
Then there's this article about Mars. Cool. One of the great questions about Mars is centered around what controlled the erosional and sedimentary features on the planet's surface and what happened to it.
Mars' surface yields some spotty paleomagnetic evidence of possible early plate tectonics (I like to think so, at least. However, it's not universally accepted and other models exist), but it's plainly evident that whatever the tectonic style of the planet, it shut down while Earth was still in the Precambrian Eon (I guess it's considered a "Supereon"?). Mars is just too small to maintain plate tectonics/convection cycles like those of Earth - the heat gradient from core to surface is too steep. I could talk all day about what I think about the formation of the giant shield volcanoes and Tharsis, but that's not what the article's about. Well, it could tie into Tharsis. But it's not directly about it.
Later on, sedimentary features developed - most strikingly, the canyons larger than any found on Earth. Whatever fluids and erosional processes that once controlled this are mostly gone now. It's now being postulated in this article that some of the channel features were carved out by lava.
I can buy this - camped in Snow Canyon State Park in Utah a couple of years ago. It admittedly started as a canyon carved by fluvial (waterflow-driven) processes, but was located proximal to a basaltic magma source as young as 20,000 years old. Eruptions there changed the course of the river - partly by building up topography in some places and carving it out in others. Redirection of waterways carved new, deeper canyons and remnants of older lava flows can be seen near the top of the present day canyon. This is a phenomenon called "inverted topography," where younger rock sits lower than older rock. This is only one way to form inverted topography, but that could be a blog post in and of itself, so maybe I'll save that for another post.
Monday, March 1, 2010
More Cool Earthquake Stuff
From BoingBoing: Chile quake changed Earth's figure axis (based on center of mass, not north-south axis) and shortened Earth's days.
Forgive me for saying this, but this is what makes earthquake science COOL. And yes, I'm definitely keeping Chile in my thoughts; a friend of mine has plans to live there for a short while after she finishes her master's degree next year so my degree of separation from the country will soon close significantly.
At the same time as I'm amazed at the pictures of quake damage and that the death toll is as small as it is, I have to mention that the somewhat unsympathetic side of me keeps clamoring about Man choosing to build cities, civilizations in these unstable areas. Chile is a smart country - they acknowledge their risks and build accordingly.
I have considerably less sympathy for folks who build homes on major fault lines and have zero idea what they're living on (yes, I'm talking about YOU, people who built mansions on the Wasatch Fault!!). Sure, it's a great view. Sure, I'd LOVE to have a mountain range as my backyard. Do I want to live on a major fault line, even if it only ruptures every several hundred years? Nope! The less frequently a fault ruptures, the less data we can gather on it and the less we know about that fault or fault system.
Forgive me for saying this, but this is what makes earthquake science COOL. And yes, I'm definitely keeping Chile in my thoughts; a friend of mine has plans to live there for a short while after she finishes her master's degree next year so my degree of separation from the country will soon close significantly.
At the same time as I'm amazed at the pictures of quake damage and that the death toll is as small as it is, I have to mention that the somewhat unsympathetic side of me keeps clamoring about Man choosing to build cities, civilizations in these unstable areas. Chile is a smart country - they acknowledge their risks and build accordingly.
I have considerably less sympathy for folks who build homes on major fault lines and have zero idea what they're living on (yes, I'm talking about YOU, people who built mansions on the Wasatch Fault!!). Sure, it's a great view. Sure, I'd LOVE to have a mountain range as my backyard. Do I want to live on a major fault line, even if it only ruptures every several hundred years? Nope! The less frequently a fault ruptures, the less data we can gather on it and the less we know about that fault or fault system.
Earthquake Frequency Stats
Here's a really good article on earthquake frequency in light of the recent quakes in Japan and Chile.
I'm not going to copy/paste anything directly into this post from that article, but I recommend reading through it. It is a strong testimony to the extremely short memory of us as a society, not to mention how uninformed the public are on earthquakes.
Many of the earthquakes studied in this statistics exercise (M 6.0-6.9) don't even make news because they occur in remote/low population areas, little damage occurs, or quakes of that magnitude occur with enough frequency that it's not unusual to the residents of the area. It's the quakes that size that hit less frequently in populated areas or cause lots of damage/kill lots of people that make the news. It's all about the social impact.
There's the matter of correlation vs. causation and the breakdown of Occam's Razor to some extent going on. Short public memory combined with 3 significant earthquakes since January causes a stir. Sure, there's a correlation. Three large quakes occurred in a short period of time. People died; it was a huge social impact.
Correlation here does not imply causation, however. It's easy to apply Occam's Razor and say, "well, they happened quickly, they must be related to each other."
Not necessarily. In this case, the better application of Occam is to say, "They correlate. They may or may not be related thanks to the large releases of energy from each quake and the resultant redistribution of stresses on portions of tectonic plate boundaries worldwide. But we cannot say causation - not enough information."
Add in the sensationalistic 2012 bullcrap, and it's easy to get swept up in the hype.
In a nutshell, sit down and think about it. Bad things and good things tend to cluster like this, but we're more prone to remember the bad things.
I'm not going to copy/paste anything directly into this post from that article, but I recommend reading through it. It is a strong testimony to the extremely short memory of us as a society, not to mention how uninformed the public are on earthquakes.
Many of the earthquakes studied in this statistics exercise (M 6.0-6.9) don't even make news because they occur in remote/low population areas, little damage occurs, or quakes of that magnitude occur with enough frequency that it's not unusual to the residents of the area. It's the quakes that size that hit less frequently in populated areas or cause lots of damage/kill lots of people that make the news. It's all about the social impact.
There's the matter of correlation vs. causation and the breakdown of Occam's Razor to some extent going on. Short public memory combined with 3 significant earthquakes since January causes a stir. Sure, there's a correlation. Three large quakes occurred in a short period of time. People died; it was a huge social impact.
Correlation here does not imply causation, however. It's easy to apply Occam's Razor and say, "well, they happened quickly, they must be related to each other."
Not necessarily. In this case, the better application of Occam is to say, "They correlate. They may or may not be related thanks to the large releases of energy from each quake and the resultant redistribution of stresses on portions of tectonic plate boundaries worldwide. But we cannot say causation - not enough information."
Add in the sensationalistic 2012 bullcrap, and it's easy to get swept up in the hype.
In a nutshell, sit down and think about it. Bad things and good things tend to cluster like this, but we're more prone to remember the bad things.
Sunday, February 28, 2010
Thoughts on Yesterday
Watched the online CBS stream coming out of the local station in Hilo yesterday afternoon, where the station's traffic cameras had been pointed seaward, attempting to capture live video of incoming tsunami waves.
Needless to say, it was a success! The camera looking across Hilo Bay had some of the best views - it was somewhat incredible to watch water quickly drain out of the bay, then back in 3-4 times. Thankfully it wasn't enough to cause much damage (pretty sure some was reported here and there, but minimal - things like docks here and there), but enough that it was easily observable.
The 2004 Sumatra earthquake was unique in that the resulting tsunami was captured in satellite images before it hit the islands. This one managed to supplant that first as we had the time to prepare, get everyone near coastal areas of the island chain calmly evacuated, and someone like me could sit on my couch in Illinois and watch the waves come in at the same time as folks in Hawaii. Scientists also proved that their models, technology, and warning system WORK. Sure, the scientists who developed the tsunami propagation models are itching to refine their programs and datasets, but we know that their model so far is fairly accurate. I believe arrival of the first tsunami was within a half an hour or so of the predicted arrival, and even before then, many people familiar with the prevailing ocean patterns around the islands could tell that there were some funky things happening prior to actual surge arrivals.
The coverage on tape is simply unprecedented. I like to think that earthquake and tsunami science took a huge step forward yesterday.
Also, here's some decent data on all of the major earthquakes since 1900. The deadliest earthquakes list is interesting and strange if not that it's more of a function of building style and location of population centers than earthquake strength. (And, at risk of making a controversial statement, humanity's intelligence with regard to building what we do where we do.)
Needless to say, it was a success! The camera looking across Hilo Bay had some of the best views - it was somewhat incredible to watch water quickly drain out of the bay, then back in 3-4 times. Thankfully it wasn't enough to cause much damage (pretty sure some was reported here and there, but minimal - things like docks here and there), but enough that it was easily observable.
The 2004 Sumatra earthquake was unique in that the resulting tsunami was captured in satellite images before it hit the islands. This one managed to supplant that first as we had the time to prepare, get everyone near coastal areas of the island chain calmly evacuated, and someone like me could sit on my couch in Illinois and watch the waves come in at the same time as folks in Hawaii. Scientists also proved that their models, technology, and warning system WORK. Sure, the scientists who developed the tsunami propagation models are itching to refine their programs and datasets, but we know that their model so far is fairly accurate. I believe arrival of the first tsunami was within a half an hour or so of the predicted arrival, and even before then, many people familiar with the prevailing ocean patterns around the islands could tell that there were some funky things happening prior to actual surge arrivals.
The coverage on tape is simply unprecedented. I like to think that earthquake and tsunami science took a huge step forward yesterday.
Also, here's some decent data on all of the major earthquakes since 1900. The deadliest earthquakes list is interesting and strange if not that it's more of a function of building style and location of population centers than earthquake strength. (And, at risk of making a controversial statement, humanity's intelligence with regard to building what we do where we do.)
Saturday, February 27, 2010
Okay . . . I'm Back
I was thinking about doing pancakes for breakfast last night, but because I'm still finding info online, 1. no pancakes, I'm eating cereal instead; and 2. I'm not going to get that much work done today. I'll get some done, but probably not till after we get some initial tsunami reports from Hawaii.
List of places under tsunami warning from NOAA. (text only)
One of my favorite people to follow on Twitter, @BadAstronomer, just RTed a very cool picture predicting the spread of the earthquake's energy worldwide (credit NOAA):
List of places under tsunami warning from NOAA. (text only)
One of my favorite people to follow on Twitter, @BadAstronomer, just RTed a very cool picture predicting the spread of the earthquake's energy worldwide (credit NOAA):
Megathrust Earthquake Offshore Maule, Chile, Magnitude 8.8
Wow. This is what happens when I decide to sleep in!
The map says 8.6 because that was the original calculated magnitude; it was revised up to 8.8 a short time after. Revisions are possible because as more time passes, more seismic stations worldwide pick up readings from the earthquake. The more seismic readings, the better scientists can analyze the nature of the earthquake and how it travels through the earth.
The beach ball today is oriented differently than the one from Japan that I described yesterday. You see a colored segment surrounded by white segments. Colored quarters of these spheres represent compression, and white quarters represent extension tension.
With a compression segment centered like this between two white segments, it's indicative of compression along the fault, or a thrust fault.
Sounds like there was a 9 foot tsunami and less than 100 confirmed dead so far. Expect these numbers to rise. My e-mail inbox is flooded with notifications of the aftershocks coming in above magnitude 5.0. The largest one so far was 6.9, and apparently as of now the tsunami warning worldwide has expanded. I expect the tsunami elsewhere could well be bigger.
As screwy as it might be, geologists get REALLY geeked out when this happens. While we hate to see death tolls, especially like what we saw with the Port-Au-Prince earthquake in January (I was in Curaçao when that happened - we didn't feel it then because we were on a dive when it would've shaken the island), the geology FASCINATES us. Earthquake prediction and mitigation is an inexact science at best. Typically, quake-prone places we know the most about have frequent, small earthquakes, like some parts of California. Those aren't places we're as worried about. The places we DO worry about are the ones where faults are quiet for a very long time, building up massive amounts of stress, then release it all at once. Since there are fewer, less frequent quakes there, we can't know as much about them.
The difference in quake frequency from place to place, even along the San Andreas Fault in California, is based in many things: structure and strength of the country rocks, their tendency toward ductile or brittle deformation under high pressure, hardness of constituent minerals (e.g. feldspar (H=6) vs. serpentine (H<2.5)), and nature/rate of movement along the fault running through the rocks.
I'm not even going to get started about some of the comments I saw on CNN's article about the Japan quake yesterday, nor the ones I'll undoubtedly be reading today. The level to which this country's lack of education about natural risks is astounding. Maybe I'll post a few gems later.
Since it's 10 am and I've been fielding earthquake data back and forth with some of my fellow scientists and I haven't yet had breakfast, I'm out.
The map says 8.6 because that was the original calculated magnitude; it was revised up to 8.8 a short time after. Revisions are possible because as more time passes, more seismic stations worldwide pick up readings from the earthquake. The more seismic readings, the better scientists can analyze the nature of the earthquake and how it travels through the earth.
The beach ball today is oriented differently than the one from Japan that I described yesterday. You see a colored segment surrounded by white segments. Colored quarters of these spheres represent compression, and white quarters represent extension tension.
With a compression segment centered like this between two white segments, it's indicative of compression along the fault, or a thrust fault.
Sounds like there was a 9 foot tsunami and less than 100 confirmed dead so far. Expect these numbers to rise. My e-mail inbox is flooded with notifications of the aftershocks coming in above magnitude 5.0. The largest one so far was 6.9, and apparently as of now the tsunami warning worldwide has expanded. I expect the tsunami elsewhere could well be bigger.
As screwy as it might be, geologists get REALLY geeked out when this happens. While we hate to see death tolls, especially like what we saw with the Port-Au-Prince earthquake in January (I was in Curaçao when that happened - we didn't feel it then because we were on a dive when it would've shaken the island), the geology FASCINATES us. Earthquake prediction and mitigation is an inexact science at best. Typically, quake-prone places we know the most about have frequent, small earthquakes, like some parts of California. Those aren't places we're as worried about. The places we DO worry about are the ones where faults are quiet for a very long time, building up massive amounts of stress, then release it all at once. Since there are fewer, less frequent quakes there, we can't know as much about them.
The difference in quake frequency from place to place, even along the San Andreas Fault in California, is based in many things: structure and strength of the country rocks, their tendency toward ductile or brittle deformation under high pressure, hardness of constituent minerals (e.g. feldspar (H=6) vs. serpentine (H<2.5)), and nature/rate of movement along the fault running through the rocks.
I'm not even going to get started about some of the comments I saw on CNN's article about the Japan quake yesterday, nor the ones I'll undoubtedly be reading today. The level to which this country's lack of education about natural risks is astounding. Maybe I'll post a few gems later.
Since it's 10 am and I've been fielding earthquake data back and forth with some of my fellow scientists and I haven't yet had breakfast, I'm out.
Friday, February 26, 2010
Ryukyu Island Earthquake Magnitude 7.0
Struck at 20:31 UTC. The map below shows that it was a strike-slip quake, or two tectonic plates sliding past each other. Two other types of earthquake typically involve a vertical component; either two plates running into each other or apart from each other.
USGS quake information here.
USGS quake information here.
Subscribe to:
Posts (Atom)
