Plenty of people are curious about Parkfield. The 6.0 in 2004 simply leaves the question of when the next one will be, how it will relate to the timing of all the others. It's still an excellent place to look at high-magnitude repeating earthquakes, and probably still one of the best places to poke around for some hints toward the holy grail of earthquake prediction.
I think that stuff is interesting, and that these are good questions, but what really makes me go hmmm about Parkfield is what happened there before 1857. All of the lists that I've ever seen of major events there with the 1857 Fort Tejon earthquake, and that average recurrence interval of 22 years is calculated from there on out. But what about beforehand? Has anybody looked into this?
The SAFOD station is about getting current earthquake information from Parkfield, but has anyone done any paleoseismological digging at the site? That would be something I'd like to see. I don't know how well a 22-year recurrence interval would show up in cross section, since that doesn't give much time for new material to accumulate on the old break, but it would answer whether or not the same pattern was going on before 1857.
I've heard a theory that the whole chain of Parkfield events is still part of the Fort Tejon aftershock sequence. That's a tantalizing thought that would accommodate the increasingly longer time between the events. If paleoseismology showed that Parkfield was quiet before 1857, it could add credence to this theory - if they're not aftershocks, something about that quake changed the conditions to make them ripe for repeated earthquakes. But if not aftershocks, that brings up the question of what specific change initiated the sequence.
But if these regular 6-pointers were just as regular before 1857, what made them tick? Surely Parkfield's location between the locked and creeping sections of the fault have something to do with it, but how so? And why did 1857's quake get so much bigger? How many 6s do we get before the next Fort Tejon?
Once I'm done with my music thesis, this is a subject about which I would like to read more. I'm hoping I can find things addressing Parkfield's past when so much attention is given to its future (if any of you know of any good ones, please let me know!), but if there isn't much out there, that's a study that really ought to be done.
Friday, February 22, 2008
Thursday, February 21, 2008
Apology
My apologies for the assumptions and general vagueness of the previous post. It was pretty idiotic of me to talk about how my impression of things was different from the statistics, while not using real statistics to back up why I might have come to those impressions. Idiotic of me, and most definitely unscientific, which is not an ok way for me to be addressing things right now. I need to catch myself doing those things early on (or be caught on them - thank you, Maria and Kim!) before it becomes something that gets in the way of my work.
I hope, though, that for the lack of calculation, I at least didn't come across as being a prejudiced kind of idiotic. If, for whatever reason, I did, I'm all the more sorry.
I hope, though, that for the lack of calculation, I at least didn't come across as being a prejudiced kind of idiotic. If, for whatever reason, I did, I'm all the more sorry.
Jumping on the gender talk bandwagon...
I have to say that I was genuinely surprised by the statistics about women in the geosciences that have been posted across the geoblogosphere this week. All logic says I shouldn't have been surprised, I guess, since I've certainly heard people talk about how the hard sciences are a boys' club, how girls are socialized to not like science, and all those similar things. Logic says people would be making these points for a reason. Not to mention I've heard similar lame/pathetic/infuriating statements about "womanyness" (to steal Eric's term) and lower aptitude in other contexts. But I was still really surprised to hear it about the geosciences in particular, and it took me a little while to put a finger on why.
One of the reasons, I think, is the geoblogosphere itself. I found out about its existence from Maria, finally stopped being chicken about commenting thanks to an entry in Kim's, blog, got into a comment-conversation with Tuff Cookie almost right away, and so on. I guess, silly me, that I assumed the non-internet version of the field would have the same proportion of intelligent, knowledgeable, and articulate female scientists to whom a lot of other people pay serious attention that the blogosphere does.
Part of it might have been the people from whom I got information (or inspiration) on the earth sciences before I decided to apply to formally study it. When I was six and totally obsessed with volcanoes, I had a video of the National Geographic special about Maurice and Katya Krafft, which I watched constantly. Katya had just as much scientific input and daring in the field (and just as much of a deathwish) as Maurice. And far more recently, when I first moved to California and wanted to go poke the faults, the book I regarded as indispensable was Finding Fault in California, by Susan Hough (who I got to meet this week - more on that in another entry). Woman geoscientists and definite authorities, both. They gave me no reason to suspect imbalance. And on a much smaller authority scale, two of the three geoscience teachers at my high school were women.
And a lot of it definitely has to do with the department I'm involved with now (I'm going to refer to it as my department, even though they haven't sent me that official letter yet). The head of the department is a woman, for one, and while there are still more men on faculty than women, it's not a hugely skewed proportion. It's even more balanced among the graduate students. My department has also gone above and beyond in terms of gender awesomeness in that there is a pre-transition female-to-male transgendered student in the department, and everyone has been incredibly respectful and accepting of him. I know there's no further statistics in that regard in the Nature article, but it doesn't strike me as something the Old Dinosaur Boys would be fans of either.
So I had this pretty concretely formed idea that the geosciences were less gender exclusive than some of the other physical sciences. In a way, I guess it's good that I've had this buildup of situations and role models that made hearing the real statistics surprising rather than old news, but that doesn't come even close to making up for how unfair and imbalanced the field really is.
One of the reasons, I think, is the geoblogosphere itself. I found out about its existence from Maria, finally stopped being chicken about commenting thanks to an entry in Kim's, blog, got into a comment-conversation with Tuff Cookie almost right away, and so on. I guess, silly me, that I assumed the non-internet version of the field would have the same proportion of intelligent, knowledgeable, and articulate female scientists to whom a lot of other people pay serious attention that the blogosphere does.
Part of it might have been the people from whom I got information (or inspiration) on the earth sciences before I decided to apply to formally study it. When I was six and totally obsessed with volcanoes, I had a video of the National Geographic special about Maurice and Katya Krafft, which I watched constantly. Katya had just as much scientific input and daring in the field (and just as much of a deathwish) as Maurice. And far more recently, when I first moved to California and wanted to go poke the faults, the book I regarded as indispensable was Finding Fault in California, by Susan Hough (who I got to meet this week - more on that in another entry). Woman geoscientists and definite authorities, both. They gave me no reason to suspect imbalance. And on a much smaller authority scale, two of the three geoscience teachers at my high school were women.
And a lot of it definitely has to do with the department I'm involved with now (I'm going to refer to it as my department, even though they haven't sent me that official letter yet). The head of the department is a woman, for one, and while there are still more men on faculty than women, it's not a hugely skewed proportion. It's even more balanced among the graduate students. My department has also gone above and beyond in terms of gender awesomeness in that there is a pre-transition female-to-male transgendered student in the department, and everyone has been incredibly respectful and accepting of him. I know there's no further statistics in that regard in the Nature article, but it doesn't strike me as something the Old Dinosaur Boys would be fans of either.
So I had this pretty concretely formed idea that the geosciences were less gender exclusive than some of the other physical sciences. In a way, I guess it's good that I've had this buildup of situations and role models that made hearing the real statistics surprising rather than old news, but that doesn't come even close to making up for how unfair and imbalanced the field really is.
Saturday, February 16, 2008
Geological Wardrobe
Despite its stratigraphic errors, I ended up ordering the Threadless Geology shirt. I put very little energy into my wardrobe except where geeky t-shirts are concerned, and I tend to design most of my own geeky t-shirts. I get really excited when I come across one that I didn't make, since it means that there are other people whose sense of geekery is on the same wavelength as mine. I'm not sure whether I should wear it on a music class-intensive (expected comments: "omg u nerd") day or a geology class-intensive (expected comments: "wtf nonconformity?!") day first.
On the topic of clothes, though, my geek sense sometimes gets the better of me. I was admittedly very very confused the first time I saw someone wearing clothes from Hollister Co.. "That town is famous for something other than aseismic creep?" I thought. Followed by, "Why is Hollister advertising surfing stuff when it's kind of inland? And San Benito County really isn't SoCal..."
Eventually, I remembered to look it up, only to find out that the clothing company has nothing to do with the Calaveras Fault's tromping grounds. This made the geek sense sad, even though it did not stop being amused by all these people making inadvertent seismology references.
But the geek sense is also a curious sense, seeking others on its wavelenght, as I mentioned before. I've therefore asked a few of the seismologists on faculty, and a few of the other grad students, if they can see people sporting that brand name without thinking of aseismic creep. To my glee, everyone I've asked makes the same instant connection that I do.
Which meant it was project time:
(Lest you assume I'm actually decent at sewing, I used clear thread on this precisely so nobody could see how the stitches might as well be a ball of string after my cats were done with it.)
This may mark the only time I buy blatantly name-brand things: to modify them for greater geek cred power. Booyah.
On the topic of clothes, though, my geek sense sometimes gets the better of me. I was admittedly very very confused the first time I saw someone wearing clothes from Hollister Co.. "That town is famous for something other than aseismic creep?" I thought. Followed by, "Why is Hollister advertising surfing stuff when it's kind of inland? And San Benito County really isn't SoCal..."
Eventually, I remembered to look it up, only to find out that the clothing company has nothing to do with the Calaveras Fault's tromping grounds. This made the geek sense sad, even though it did not stop being amused by all these people making inadvertent seismology references.
But the geek sense is also a curious sense, seeking others on its wavelenght, as I mentioned before. I've therefore asked a few of the seismologists on faculty, and a few of the other grad students, if they can see people sporting that brand name without thinking of aseismic creep. To my glee, everyone I've asked makes the same instant connection that I do.
Which meant it was project time:
(Lest you assume I'm actually decent at sewing, I used clear thread on this precisely so nobody could see how the stitches might as well be a ball of string after my cats were done with it.)
This may mark the only time I buy blatantly name-brand things: to modify them for greater geek cred power. Booyah.
Friday, February 15, 2008
Slow global warming - stop earthquakes!
Last Thursday's journal club was something of a milestone for me - my first even semiformal presentation on a scientific topic since high school, and for an audience of people who already have degrees in (or have already partly completed degrees in, at least) seismology. Journal club is laid back and conversational and not for any sort of grade or credit, which really gave me no good reason to be worrying about it, but I was worried nevertheless.
My job was to summarize seismological happenings in Nature since December, of which there have not been very many. Of the two earthquake articles I found (there was also a volcano article, which I did not realize was fair game until after the presentation), I went a little more in-depth on one summarizing an experiment simulating stick slip events in fault gauge particles using glass beads and low-frequency sound waves. The experimenters built a rig that applied constant stress to the beads, and could apply pulses or prolonged sounds if desired. Without the sound waves, the recurrence interval and stress drop of the stick slip events was constant and predictable, but as soon as one pulse was thrown into the mix, the recurrence interval became unpredictable and the stress drop fluctuated more. The aim was to try and see how a bombardment of long-distance seismic waves across an unrelated fault triggers new quakes, and to see if there was any pattern to it that could be used for the sake of predictions. There was no pattern, and I had a few questions about the method (such as the size of the beads, or whether or not the direction from which the pulses came made a difference on the results), but the consensus of everyone at the meeting was that these were valid questions that hopefully were covered in some supplement to the article somewhere, since these things really shouldn't have been left out.
And it turns out that worrying was, as I should have expected, not a thing I needed to be doing. People asked questions after I was finished, which answered as best I could, and then there was some further discussion of long-distance triggering. It didn't seem to be any more or any less discussion and questioning than after anyone else's presentation that I've seen so far, and one of the faculty told me it was a "very good kind of unremarkable," and that I would have definitely been told if I'd screwed up. Now that I know I've done well once, the next time should be easier.
The other person who presented last Thursday chose to focus in on a paper dealing with carbon dioxide released from faults during large earthquakes. The theory is that there is enough friction in larger quakes to melt a small amount of the rock in the fault, which releases gas. I thought it was an interesting article, but the way the title was worded made it sound like a disastrous global-warming-related phenomenon. I forget the exact wording, but at first glance, it seemed like the article might actually be some far-fetched thing about how faults, when just sitting there, are spewing greenhouses gases. I was glad that was not the actual content, but I have to wonder if the title was carefully formulated to grab attention in a time when global warming is such a focus. It was also certainly good for a long string of "stop plate tectonics" jokes, though we all agreed that volcanic emissions should be targeted for reduction first...
My job was to summarize seismological happenings in Nature since December, of which there have not been very many. Of the two earthquake articles I found (there was also a volcano article, which I did not realize was fair game until after the presentation), I went a little more in-depth on one summarizing an experiment simulating stick slip events in fault gauge particles using glass beads and low-frequency sound waves. The experimenters built a rig that applied constant stress to the beads, and could apply pulses or prolonged sounds if desired. Without the sound waves, the recurrence interval and stress drop of the stick slip events was constant and predictable, but as soon as one pulse was thrown into the mix, the recurrence interval became unpredictable and the stress drop fluctuated more. The aim was to try and see how a bombardment of long-distance seismic waves across an unrelated fault triggers new quakes, and to see if there was any pattern to it that could be used for the sake of predictions. There was no pattern, and I had a few questions about the method (such as the size of the beads, or whether or not the direction from which the pulses came made a difference on the results), but the consensus of everyone at the meeting was that these were valid questions that hopefully were covered in some supplement to the article somewhere, since these things really shouldn't have been left out.
And it turns out that worrying was, as I should have expected, not a thing I needed to be doing. People asked questions after I was finished, which answered as best I could, and then there was some further discussion of long-distance triggering. It didn't seem to be any more or any less discussion and questioning than after anyone else's presentation that I've seen so far, and one of the faculty told me it was a "very good kind of unremarkable," and that I would have definitely been told if I'd screwed up. Now that I know I've done well once, the next time should be easier.
The other person who presented last Thursday chose to focus in on a paper dealing with carbon dioxide released from faults during large earthquakes. The theory is that there is enough friction in larger quakes to melt a small amount of the rock in the fault, which releases gas. I thought it was an interesting article, but the way the title was worded made it sound like a disastrous global-warming-related phenomenon. I forget the exact wording, but at first glance, it seemed like the article might actually be some far-fetched thing about how faults, when just sitting there, are spewing greenhouses gases. I was glad that was not the actual content, but I have to wonder if the title was carefully formulated to grab attention in a time when global warming is such a focus. It was also certainly good for a long string of "stop plate tectonics" jokes, though we all agreed that volcanic emissions should be targeted for reduction first...
Monday, February 11, 2008
Igneous Sounds
As requested, here are the five "igneous sounds" I came up with for my computer music class. There was an actual "composition" that used these sounds, but it was the kind of thing where the professor said, "Take five minutes to turn those sounds into a piece," and I chucked the things into the sequencer in somewhat random order. I was amazed that the professor liked it as much as he did, since I kind of thought it was crap. But here are the five component sounds.
Granite
Quartz left channel, frequency 500 Hz
Orthoclase right channel, frequency 200 Hz
Entire envelope played at one cycle per minute
Granodiorite
Plagioclase left channel, frequency 600
Quartz right channel, frequency 150
Entire envelope played at one cycle per three seconds
Diorite
Amphibole left channel, frequency 200
Plagioclase right channel, frequency 800
Entire envelope played at once cycle per ten seconds
Gabbro
Pyroxene left channel, frequency 180
Plagioclase right channel, frequency 120
Entire envelope played at one cycle per three seconds
Peridotite
Olivine left channel, frequency 400
Pyroxene right channel, frequency 600
Entire envelope played at two cycles per second
Considering the pace of the seminar, I doubt I'll get to use these again in the actual class, but if there'd ever be a reason for me to write a non-assignment electronic composition, sonifying geo-geekery would be a darn good one. I have some further sonification ideas percolating for the patches we've been given to work with this week, so I may have some different stuff to show soon.
Granite
Quartz left channel, frequency 500 Hz
Orthoclase right channel, frequency 200 Hz
Entire envelope played at one cycle per minute
Granodiorite
Plagioclase left channel, frequency 600
Quartz right channel, frequency 150
Entire envelope played at one cycle per three seconds
Diorite
Amphibole left channel, frequency 200
Plagioclase right channel, frequency 800
Entire envelope played at once cycle per ten seconds
Gabbro
Pyroxene left channel, frequency 180
Plagioclase right channel, frequency 120
Entire envelope played at one cycle per three seconds
Peridotite
Olivine left channel, frequency 400
Pyroxene right channel, frequency 600
Entire envelope played at two cycles per second
Considering the pace of the seminar, I doubt I'll get to use these again in the actual class, but if there'd ever be a reason for me to write a non-assignment electronic composition, sonifying geo-geekery would be a darn good one. I have some further sonification ideas percolating for the patches we've been given to work with this week, so I may have some different stuff to show soon.
Sunday, February 10, 2008
Adventures in Sonification
I'm taking the last of the seminars required for my music MA this quarter - a class in computer music composition, as in Serious Art Music rather than just how to use midi or how to create the kind of electronica that's actually popular with listeners. This is really not a type of music I enjoy aesthetically. No matter how interesting the theory may be behind it, or how well the composer may write about his own piece, most of the pieces I've actually heard from this genre (and all of the ones we've listened to in this particular class) just haven't appealed to me, or have made me really want to turn the music off. (The ones I want to turn off, coincidentally, are the ones the professor declares as particularly beautiful to his ear.)
But for this seminar, I have to write that type of music. It makes sense, I suppose, as part of a thorough education for an academic composer, but it still wasn't appealing to me even when I thought I was going to be an academic composer. Yet at the same time, there's something liberating about being required to produce music in a style I know I won't want to listen to - I end up stressing over the sonic outcome less, which gives me more of an opening to mess around with concepts that are intellectually appealing (read: geeky) and not have to dismiss any of them for not sounding like I'd hoped they'd sound.
The way the assignments have been going so far is that the professor gives us a pre-constructed patch in a sound synthesis program called Max/MSP, and we have to tweak the parameters to produce different sounds from that patch, which we then record and toss together into a brief piece. Last week, the main patch we worked with involved drawing sound envelopes onto a grid, picking a speed and amplitude, then running a sine wave through it.
Last week also happened to be the week when our mineralogy class got the tour of the department's various microscope facilities. Coming from spending time the previous night drawing squiggles on the envelope grid in Max/MSP, the graphed output from powder diffraction looked an awful lot like some of those sound envelopes. The next course of action for the music homework seemed obvious.
So, I made five very basic "igneous sounds" (granite, granodiorite, diorite, gabbro, and peridotite). The patch only had two overlapping envelopes, so I couldn't include every mineral in each rock, only the two predominant components. Max/MSP gives you the option to program in very specific points on the envelope, so I could have made exact matches between the powder diffraction graph and the envelope, rather than drawing in an approximation as I actually did; the reason I didn't go exact is because I knew the professor would take all of two minutes to look at it, so time that could have been spent on specificity here was better spent elsewhere, such as on actual mineralogy, or on my thesis. I based the envelope amplitudes on the percentage of that mineral in the whole rock (for the "granite" sound, I set the amplitude for the "orthoclase" envelope at 500 and the "quartz" envelope at 200), though I experimented a little bit with how to show the percentages (the "diorite" sound had the "plagioclase" envelope at 170 and the "amphibole" envelope at 120). I didn't have any rhyme or reason, though, for the amount of time I told the program to take to play through the envelopes. I varied those because the professor assigned us to make sounds of different lengths. Now that I think about it, I could have determined the speed based on viscosity, or I could have differentiated based on speed of cooling, playing the felsic envelope quickly for rhyolite and slowly for granite.The rhythms created by the overlapping envelopes were pretty interesting, particularly for the slower sounds, and the pitches turned out surprisingly consonant/tonal. (Too consonant for my professor's taste, it turns out. He remarked on how "harmonic" it was, then made the next week's assignment involve only unpitched sound.)
I came into the first meeting of that music seminar wondering how I might be able to bring geological stuff into those assigned compositions, and I'm pretty pleased with how this tweaking of envelopes worked out. All the more incentive to try and come up with further ways to do so, as I learn more computer music techniques, not to mention more about the science I'm trying to portray with those sounds.
But for this seminar, I have to write that type of music. It makes sense, I suppose, as part of a thorough education for an academic composer, but it still wasn't appealing to me even when I thought I was going to be an academic composer. Yet at the same time, there's something liberating about being required to produce music in a style I know I won't want to listen to - I end up stressing over the sonic outcome less, which gives me more of an opening to mess around with concepts that are intellectually appealing (read: geeky) and not have to dismiss any of them for not sounding like I'd hoped they'd sound.
The way the assignments have been going so far is that the professor gives us a pre-constructed patch in a sound synthesis program called Max/MSP, and we have to tweak the parameters to produce different sounds from that patch, which we then record and toss together into a brief piece. Last week, the main patch we worked with involved drawing sound envelopes onto a grid, picking a speed and amplitude, then running a sine wave through it.
Last week also happened to be the week when our mineralogy class got the tour of the department's various microscope facilities. Coming from spending time the previous night drawing squiggles on the envelope grid in Max/MSP, the graphed output from powder diffraction looked an awful lot like some of those sound envelopes. The next course of action for the music homework seemed obvious.
So, I made five very basic "igneous sounds" (granite, granodiorite, diorite, gabbro, and peridotite). The patch only had two overlapping envelopes, so I couldn't include every mineral in each rock, only the two predominant components. Max/MSP gives you the option to program in very specific points on the envelope, so I could have made exact matches between the powder diffraction graph and the envelope, rather than drawing in an approximation as I actually did; the reason I didn't go exact is because I knew the professor would take all of two minutes to look at it, so time that could have been spent on specificity here was better spent elsewhere, such as on actual mineralogy, or on my thesis. I based the envelope amplitudes on the percentage of that mineral in the whole rock (for the "granite" sound, I set the amplitude for the "orthoclase" envelope at 500 and the "quartz" envelope at 200), though I experimented a little bit with how to show the percentages (the "diorite" sound had the "plagioclase" envelope at 170 and the "amphibole" envelope at 120). I didn't have any rhyme or reason, though, for the amount of time I told the program to take to play through the envelopes. I varied those because the professor assigned us to make sounds of different lengths. Now that I think about it, I could have determined the speed based on viscosity, or I could have differentiated based on speed of cooling, playing the felsic envelope quickly for rhyolite and slowly for granite.The rhythms created by the overlapping envelopes were pretty interesting, particularly for the slower sounds, and the pitches turned out surprisingly consonant/tonal. (Too consonant for my professor's taste, it turns out. He remarked on how "harmonic" it was, then made the next week's assignment involve only unpitched sound.)
I came into the first meeting of that music seminar wondering how I might be able to bring geological stuff into those assigned compositions, and I'm pretty pleased with how this tweaking of envelopes worked out. All the more incentive to try and come up with further ways to do so, as I learn more computer music techniques, not to mention more about the science I'm trying to portray with those sounds.
Sunday, February 3, 2008
Meet the Faultcats
So, Callan Bentley at NOVA Geoblog posted an incredibly cute picture of his feline lab assistant, which has inspired me to share photos of my own fuzzy seismically-inclined monsters.
This is Andreas:
He knows what he's named after, and he clearly feels it is his responsibility to learn as much about that namesake as he can.
He's had these tendencies from a very young age:
(Andreas and his five littermates were born in my apartment this past summer. Their mother was a stray that I took in, not knowing she was pregnant. The mommycat and four of the other babies have since been adopted, but I decided to keep Andreas and his brother Garlock. He's three weeks old in this photo, and he crawled onto the computer all by himself.)
While it's cute to see Andreas studying, it's not the most opportune thing when he decides to read the same thing I'm reading while I'm reading it.
Garlock has similar studious tendencies, though he seems to have taken more to ethnomusicology than to the earth sciences. However, he is afraid of my camera, so I have many fewer pictures of him in general, let alone while he's "working." This is one of the better ones (Garlock's the black one):
(The Siamese on the right is Jacinto, who is, believe it or not, part of the same litter as Andreas and Garlock. Guess what the other three kittens were named.)
This is Andreas:
He knows what he's named after, and he clearly feels it is his responsibility to learn as much about that namesake as he can.
He's had these tendencies from a very young age:
(Andreas and his five littermates were born in my apartment this past summer. Their mother was a stray that I took in, not knowing she was pregnant. The mommycat and four of the other babies have since been adopted, but I decided to keep Andreas and his brother Garlock. He's three weeks old in this photo, and he crawled onto the computer all by himself.)
While it's cute to see Andreas studying, it's not the most opportune thing when he decides to read the same thing I'm reading while I'm reading it.
Garlock has similar studious tendencies, though he seems to have taken more to ethnomusicology than to the earth sciences. However, he is afraid of my camera, so I have many fewer pictures of him in general, let alone while he's "working." This is one of the better ones (Garlock's the black one):
(The Siamese on the right is Jacinto, who is, believe it or not, part of the same litter as Andreas and Garlock. Guess what the other three kittens were named.)
Saturday, February 2, 2008
The Tsunami and the Whale
Now that I've pretty much caught up with the load of work on which I procrastinated even more than usual due to last weekend's concerts, I can get back to interacting with the internet rather than just lurking. At least for the time being...
I have two weeks of Journal Club to catch up on here. Both of these weeks involved several people doing overviews of recent journal contents. This broke with the alternating schedule of small papers one week, big paper another week because the professor scheduled to present the big paper had a conflict. This meant I couldn't use reading the seismology paper as an excuse to further procrastinate on the electronic music homework, but it also meant more of an overview of recent research that I'd like to be reading but don't have the time for just yet, no thanks to the impending thesis and comprehensive exams.
The main paper we looked at this week dealt with small earthquakes only, which seems to be a relatively unpopular thing to write about. It makes perfect sense that people would want to focus on the Big Ones, since those are the events that effect society at large and that totally redo the stress balance on a fault system in one fell swoop, but the catalog of hard data (rather than historical description of effects) doesn't really include many of these for any given region. But there are plenty of small ones, and I'm sure there are plenty of studies that could be done on small ones that don't just relate them to big ones. The particular focus of the paper we looked at on Thursday was direction of slip (as in unilateral versus bilateral) and how that effected aftershocks. The largest quake discussed in the paper was a magnitude 4.1, which put most of the aftershocks into the unfeelable range. Looking at a few isolated 4-ish quakes, there did seem to be a correlation between directivity and aftershocks, with unilateral quakes having more aftershocks, which were mostly located within 70 degrees of the rupture plane. Bilateral quakes had fewer aftershocks in a less-confined space. The final example in the paper was a cluster of high-3 low-4 quakes up in the vicinity of the Calaveras Fault and at a pretty deep depth, and that's where the model got a little tricky. Whether each event in the cluster counted as an aftershock of the largest event previous to it or whether the ones close in magnitude counted as separate events was unclear, but those of us in the discussion agreed that the way these events were considered would make a difference in the conclusions. Furthermore, it seemed like the people conducting the study were inconsistent in what they treated as an aftershock versus a separate event, and it looked suspiciously like they might have done this to fit into the 70-degree angle measurement. We all agreed the paper would have been much stronger without the example of the cluster, both for the consistency thing, and also because a different configuration of stress is needed to set off a cluster versus an isolated event and its aftershocks.
Out of all the papers summarized last week, the one that was most interesting to me looked at postseismic slip between a mainshock and a large aftershock. I don't remember a huge number of details about the paper(people go through papers quickly during summary weeks - I've been thinking of asking the person who picked this one where I can find the whole thing), but it focused on a series of events in Japan. The study found a substantial amount of postseismic slip after the mainshock, directed toward the eventual location of the aftershock. These events went down the subduction zone rather than along it. I have to wonder what implications, if any, this observation would have on a creeping strike-slip fault. Could a rupture starting ahead of a creeping section and moving toward it stop where the creep starts, speeding up the rate of creep in the hours following the quake, and eventually set off another event on the other side of the creeping section? I'll definitely be looking to see if there are papers about this.
The other main paper we looked at last week had to do with inferring the size and shape of the area of seafloor displacement in a tsunami-generating earthquake by looking at the tsunami waves and inverting the data. I wasn't quite clear on how this worked based on the brief explanation in the discussion, but it was still a memorable discussion due to an amazing mental image. The professor explaining the paper was describing how DART tsunameters work, and how, unlike buoys, they're stuck to the ocean floor and won't pick up water column changes from surface/storm waves. "Only tsunamis set these things off," he said. "Or if a whale died and fell on one, that might do it, too."
Whale + tsunameter. Is that not fantastic? The mental image kept popping into my head all weekend, even at such inopportune times as the dress rehearsal for the concert (it was all I could do to not crack up). With such persistent visual thoughts, there was really only one thing I could do:
(I'm aware the big wooshy splash thing should be coming off of the whale's whole body. I just became aware too late to undo the coloring. Bleaugh.)
I think I'm going to give the original copy of this to the professor who made the comment, since it's all his fault.
I have two weeks of Journal Club to catch up on here. Both of these weeks involved several people doing overviews of recent journal contents. This broke with the alternating schedule of small papers one week, big paper another week because the professor scheduled to present the big paper had a conflict. This meant I couldn't use reading the seismology paper as an excuse to further procrastinate on the electronic music homework, but it also meant more of an overview of recent research that I'd like to be reading but don't have the time for just yet, no thanks to the impending thesis and comprehensive exams.
The main paper we looked at this week dealt with small earthquakes only, which seems to be a relatively unpopular thing to write about. It makes perfect sense that people would want to focus on the Big Ones, since those are the events that effect society at large and that totally redo the stress balance on a fault system in one fell swoop, but the catalog of hard data (rather than historical description of effects) doesn't really include many of these for any given region. But there are plenty of small ones, and I'm sure there are plenty of studies that could be done on small ones that don't just relate them to big ones. The particular focus of the paper we looked at on Thursday was direction of slip (as in unilateral versus bilateral) and how that effected aftershocks. The largest quake discussed in the paper was a magnitude 4.1, which put most of the aftershocks into the unfeelable range. Looking at a few isolated 4-ish quakes, there did seem to be a correlation between directivity and aftershocks, with unilateral quakes having more aftershocks, which were mostly located within 70 degrees of the rupture plane. Bilateral quakes had fewer aftershocks in a less-confined space. The final example in the paper was a cluster of high-3 low-4 quakes up in the vicinity of the Calaveras Fault and at a pretty deep depth, and that's where the model got a little tricky. Whether each event in the cluster counted as an aftershock of the largest event previous to it or whether the ones close in magnitude counted as separate events was unclear, but those of us in the discussion agreed that the way these events were considered would make a difference in the conclusions. Furthermore, it seemed like the people conducting the study were inconsistent in what they treated as an aftershock versus a separate event, and it looked suspiciously like they might have done this to fit into the 70-degree angle measurement. We all agreed the paper would have been much stronger without the example of the cluster, both for the consistency thing, and also because a different configuration of stress is needed to set off a cluster versus an isolated event and its aftershocks.
Out of all the papers summarized last week, the one that was most interesting to me looked at postseismic slip between a mainshock and a large aftershock. I don't remember a huge number of details about the paper(people go through papers quickly during summary weeks - I've been thinking of asking the person who picked this one where I can find the whole thing), but it focused on a series of events in Japan. The study found a substantial amount of postseismic slip after the mainshock, directed toward the eventual location of the aftershock. These events went down the subduction zone rather than along it. I have to wonder what implications, if any, this observation would have on a creeping strike-slip fault. Could a rupture starting ahead of a creeping section and moving toward it stop where the creep starts, speeding up the rate of creep in the hours following the quake, and eventually set off another event on the other side of the creeping section? I'll definitely be looking to see if there are papers about this.
The other main paper we looked at last week had to do with inferring the size and shape of the area of seafloor displacement in a tsunami-generating earthquake by looking at the tsunami waves and inverting the data. I wasn't quite clear on how this worked based on the brief explanation in the discussion, but it was still a memorable discussion due to an amazing mental image. The professor explaining the paper was describing how DART tsunameters work, and how, unlike buoys, they're stuck to the ocean floor and won't pick up water column changes from surface/storm waves. "Only tsunamis set these things off," he said. "Or if a whale died and fell on one, that might do it, too."
Whale + tsunameter. Is that not fantastic? The mental image kept popping into my head all weekend, even at such inopportune times as the dress rehearsal for the concert (it was all I could do to not crack up). With such persistent visual thoughts, there was really only one thing I could do:
(I'm aware the big wooshy splash thing should be coming off of the whale's whole body. I just became aware too late to undo the coloring. Bleaugh.)
I think I'm going to give the original copy of this to the professor who made the comment, since it's all his fault.
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