Category Archives: General Science

Are Rocks like Springs? A Video Demonstration

Today I was getting a demo in the lab ready for a tour group and decided to try shooting a quick, unscripted bit on rocks as springs.  There are a few generalized statements in here, but overall it is a first try at a public education video.  Comments welcome!

Exploring Scientific Computing at SciPy 2014

Texas Campus

This past week I've been in Austin, TX attending SciPy 2014, the scientific Python conference.  I came in 2010 for the first time, but hadn't been able to make it back again until this year.  I love this conference because it gives me the chance to step away from work on my PhD and distractions of hobby projections to focus on keeping up with the world of scientific computing with Python.  I try to walk the fine line between being a researcher, engineer, and programmer everyday.  That means that it is easy to fall behind the state of the art in any one of those, and conferences like this are my way to getting a chance to learn from the best.

SciPy consists of tutorials, the conference, and sprints:

The first two days were tutorials in which I got to learn about using interactive widgets in iPython notebooks, reproducible science, image processing, and Bayesian analysis.  I see lots of things that I can apply in my research and teaching workflows!  Interactive notebooks are one of the last things that I was wishing for from the Mathematica notebooks.

The next three days were talks in which we got to see the newest software developments and creative applications of Python to scientific problems.  I, of course, gravitated to the geophysics oriented talks and even ran into some people with common connections.  It was during the conference that I gave my poster presentation.  I knew that the poster focused more on the application of Python to earthquake science than any earth-shaking (pun-intended) software development.  There were a few on the software side that wondered why I was there (as expected), but the poster was generally very well received.  Again I had several chance encounters with people from Google and other companies that had similar backgrounds or were just very interested in earthquakes!

The final two days (I'm writing this on the last day) were sprints.  These are large pushes to further develop the software while a critical mass of experts are in one location.  I'm still new enough to these massive open-source projections (on the development side at least) that I wasn't incredibly useful, but the reception of the developers was great!  Everyone was excited if you wanted to help and would spend as much time as needed to get you up and running.  During the sprints I've been following a fix for an issue that has recently caused problems in my plotting.  I also fixed a tiny issue (with help) and had my first pull request accepted.  For software people these are tiny steps, but for someone coming from just developing in-house purpose-designed tools.... it was an hit of the open-source collaboration drug.

Lastly, I worked on a project of my own during the evenings.  During the 2010 conference I worked with a friend to make a filter remove the annoying vuvuzela sound from the World Cup audio.  This year I've been making a fun earthquake visualization tool.  You'll be seeing it here on the blog, and may have already seen it if you follow me on twitter.  I learned a lot during this year's SciPy 2014, got to spend time with other alums of OU Meteorology, and meet some new folks.  Next on the blog we'll be back to some radar or maybe a quick earthquake discussion!

Gravitational Tricks: Lagrange Points and Orbiting at Puzzling Speeds

The orbital path of ISEE3 from launch to near present.

The orbital path of ISEE3 from launch to near present.

Last time I talked about a team trying to capture and reuse the ISEE3 satellite (here).  The team has received lots of telemetry lately, determined the rotation speed of the satellite, and even had an amateur radio operator receive the satellite!  While all of this is going on, they must rapidly plan out what orbit they wish to enter.  The most discussed orbit is termed ESL1, the Earth-Sun system Lagrangian point #1.  Lagrange points an interesting phenomena that I thought worth a short discussion.

When we think of orbits, traditionally we consult Kepler's laws.  These "laws" are 3 simple rules that were written down between 1609 and 1619 by Johannes Kepler.  I won't discuss them at length, because there are already many great sources to learn about Kepler's Laws and their application.  The thing we want to draw from them is that an object orbiting closer to the Sun (say Venus), will have to travel faster to satisfy the laws of nature.  In doing so it will orbit the Sun more times than the Earth will in the same amount of time.  Venus will in fact orbit the sun 1.6 times during 1 orbit of the Earth!

Let's say we place a satellite far away from the Earth, between the Earth and sun.  the satellite will orbit slightly faster than the Earth.  Over a period of time it will be on the opposite side of the Sun and we won't be able to communicate.  Eventually it will come around and lap the Earth! This isn't desirable, but we can use Lagrange points to solve this problem.

The simple laws of orbital mechanics that we have considered thus far are only valid for a simple problem with two objects (Earth and Sun or Earth and Satellite).  We have we three bodies though, the Earth, the Sun, and the satellite! Three body problems are generally sticky to solve, but we have an advantage.  The mass of a satellite is small compared to the mass of the Earth and the mass of the Sun (unless it's the Death Star).   We can ignore the small mass of the satellite as solve what is known as the restricted three body problem.  There are a few interesting points in space, the Lagrange points, at which the gravitational pull from the Sun and Earth are superimposed on each other to give the satellite the same orbital speed as the Earth!

The L1 point is where ISEE3 may end up, so let's look at it.  The satellite will be above the Earth at an altitude of 1.5 million km (932,000 miles), towards the Sun.  At this point, the two body mechanics say that the satellite will orbit the Sun faster than the Earth.  Adding in the complications of the three body problem, we see that the gravitational tug of the Earth towards the Earth,  away from the Sun is canceling out just enough of the Sun's pull to make the satellite orbit at the same angular speed as the Earth.  How useful!

There are other Lagrangian points as well (L2-L5), but we won't discuss them here, other than to say that a similar explanation can be given for each.  L4 and L5 are particularly interesting because they are inherently stable and hence lots of objects get caught there.  There are objects in Earth-Sun L4/L5 and Earth-Moon L4/L5.

Lagrange Points of the Earth-Sun system (Image: Wikipedia)

Lagrange Points of the Earth-Sun system (Image: Wikipedia)

Generally satellites are placed in a small orbit around the L1 point for several reasons, including that it isn't inherently very stable.  The ISEE3 team will have to execute a rather complex series of maneuvers to get to L1 again, using the pull of the moon and making a very close pass that comes within 10's of km of the surface of the moon.  Time is of the essence, as the longer the wait the more they must change the speed of the craft (referred to as Delta V in the engineering jargon).  The ship only has about 150m/s of Delta V left before it runs out of fuel.  It'll take up to 1/3 of that to reposition the satellite, depending on how long the team must wait.

That's the quick and dirty view of Lagrangian points.  I hope this was interesting and helps you understand space exploration, or your addiction to Kerbal Space Program a little more!

Exploding Ice and Rock - Booms Heard a Result of "Cryoseisms"

Ice Hanging From Rock

UPDATE 1/13/14: Frost-quake creates 100ft long crack here.

Over the past few days (starting around Christmas eve), there have been reports of large booming sounds associated with minor ground shaking across the northern states, as well as in Canada.  The Toronto events have a nice string of tweets that are associated with them as well.  Are these really explosions? Earthquakes? Sonic booms? The truth, as it turns out, is a rare event that produces what are known as "cryoseisms".  Oddly enough, these "frostquakes", as they are commonly known, have been discussed in the literature since about 1818!  Having a background in both meteorology and geophysics, cryoseisms are just one example of how closely related to two fields are.

So, what happens to produce such loud and potentially startling events? It's all about ice.  Cryoseisms occur when there are seasonal frost conditions, no insulating blanket of snow, lots of rain/thaw to saturate the ground, and a sharp drop in temperature.

Surface water penetrates into sufficiently permeable soil/rocks, but then is rapidly frozen with a fast drop in surface temperature.  Normally temperature drops slowly enough that the ice gradually freezes, giving the surrounding soil/rock time to adjust.  When really fast temperature drops occur and freezing is rapid, the surrounding areas are stressed by the expanding force of the ice.

The freezing process is actually a very powerful mechanism, and is one of the geologist's favorite ways to explain physical weathering of large boulders.  Freeze/thaw cycling has even been used as a quarrying technique in granite!

Expansion during this rapid freezing of infiltrated ground water stores energy in the surrounding rock/soil, like a spring, until..... BAM! Failure occurs in much the same way faults fail.  Here the driving force isn't tectonic though.

Cryoseisms can do light damage to structures in the immediate vicinity, but their intensity falls off very quickly with distance.  For the seismology buffs out there, the zero focal depth produces lots of surface waves, but these events are generally not recorded on seismic networks.

Want to know more about cryoseisms? The literature isn't too robust, but check out Barosh (2000), Nikonov (2010), and Voss & Herrmann (1980) for some starting points!

*Cryoseism is also used to refer to earthquakes at the base of glaciers as well.  That's a whole other story for another day!

 

Favorite Books and Products of 2013

This year, like every other, was full of lots of great, okay, and no so good things. Being the list-oriented person that I am, it seemed appropriate to list out great things of the year. While there were many things that could go here (favorite trips, etc), I thought keeping with the orientation of the blog we should look at the favorite books and products of the year. Not all of these came out in 2013, but I discovered them all in 2013. Without further delay:

Favorite Books

In Suspect TerrainIn Suspect Terrain - John Mcphee
This book reads like a novel, but gives massive geologic context. It is part of a series that I will continue reading this year. If you are curious about the geologic history of the east, this gives a driving cross-section and great context.

Scientific PresentationsThe Craft of Scientific Presentations - Michael Alley I was fortunate enough to attend my 2nd Michael Alley workshop this year and gained much from both it and his book. Dr. Alley is a phenomenal person that is full of energy. His presentation advice helped me give an AGU talk, as well as successfully pass my candidacy exams (those should probably be posts).

EE 101Electrical Engineering 101 - Darren Ashby I've seen this book for quite some time, but decided to give it a read and see what it was like. Overall it was a great intro to electronics for new-comers and a good review for those who, like me, perform lots of electronics hobby work, but are not professional engineers. A few of the analogies were somewhat wrong at anything more than the basic level, but that's what they were there for.

GuesstimationGuesstimation: Solving the World's Problems on the Back of a Cocktail Napkin - Lawrence Weinstein A fun read that helps speed up your order of magnitude estimation capabilities. These were great lunch-hour exercises.

Command and Control

 

Command and Control: Nuclear Weapons, the Damascus Accident, and the Illusion of Safety - Eric Schlosser Having lived in Arkansas for most of my life, this book was of interest to me. I was quite surprised at just how unsafe much of the nuclear arsenal was and how many close calls we have had.

Feynman's RainbowFeynman's Rainbow: A Search for Beauty in Physics and in Life - Leonard Mlodinow Recommended to me by a professor in the department, this was a quick read that gave an outside look at the life of Richard Feynman from one of his colleagues. A must for any Feynman fan or general physics reader.

Data PointsData Points: Visualization That Means Something - Nathan Yau Another stellar book from Natan Yau of flowingdata.com. Great advice on presenting complex data in an easy to digest form.

Zen

 

Zen and the Art of Motorcycle Maintenance - Robert M. Pirsig Sometimes I will read a classic, and this did not disappoint. Very quotable and very enjoyable.

 

Favorite Products

Timbuk2Timbuk2 Classic Messenger Bag I didn't want to carry my leather briefcase throughout Italy and Holland this summer, so I ended up with this bag. I can't say enough about how durable it is and what a great traveling companion it makes. I have notice many geoscience folks carry these and believe that they should sponsor AGU.

Blackwing 602Palomino Blackwing 602 Pencils A post in the "How I Work Series" mentioned these and I must say that they are the darkest pencils I've seen. I generally use pen in my notebooks, but these are great replacements.

Beaglebone

 

Beaglebone Black This is the new small/embedded computer design. I'm implementing them in my infrasound bucket project and in a few others.

Hakko

 

Hakko FX-888D Soldering Station This is my new go-to soldering station for those of us on a budget.

 

USRP Software Defined Radios While expensive, I got to use some of these in a recent project and make a radar out of them!
USRP

What did I miss?

Earthrise - 45 Years Ago Today

Earthrise Photograph

The famous "Earthrise" photograph.

On December 24, 1968 one of the most powerful photographs of our time was captured. Today being the 45th anniversary of this event, I thought a brief look back would be fitting. The crew of Apollo 8 (Borman, Anders, and Lovell) were just finishing their fourth lunar orbit when they saw an awe inspiring sight. Due to a roll maneuver being executed by the spacecraft, the Earth came into view out of the window. As the astronauts were just coming around from the far-side, the Earth was rising over the lunar terrain! This was a sight that nobody had seen before. There was a scramble for film, first a black and white photograph, then finally a color photograph as the capsule rotated further and the event came into view of another window. Listening to the crew conversation is very interesting as they hurry to photograph the event with their Hasselblad 500EL. The "Earthrise photo" is more officially known as NASA photo AS8-14-2383.

The scientific visualizations team from NASA have done a fantastic job putting together a short video showing the events that transpired with syncronized crew voice recordings. By using photos from the recent Lunar Reconnisance Orbited (LRO) and a timed camera on Apollo 8 they have even determined the exact orientation of the spacecraft during these events. I highly recommend watching it! This greatly reminds us of the sentiment Eugene Cernan expressed later in the program: "We went to explore the moon, and in fact discovered the Earth."

Field Camp - The Final Week

The final week of field camp consisted of a swap between geology/geophysics students, preparation of final reports, and a final presentation.

For the first day (Monday) of the geology/geophysics swap I was helping the geologists with my homebrew resistivity rig.  After some small problems in the morning the device cooperated, and we took a like across a fault, seeing massive jumps in conductivity over the gouge area.  The second day I was actually out with the geology professors hand mapping some of the surface geology in the area.  Tom and Neil were very instructive and were able to measure a strike and dip on things that very few would term 'outcrop'.  Nonetheless the data plotted nicely!

After the mapping came independent projects and final reports.  Cullen and I decided to collect a gravity line across the dry union fault near Salida (the area of the first field trip).  I ended up staying at camp to help the geologists process their data and Cullen went with Guang to collect the line.  The results were stunning and the calculated fault dip angle is 87 degrees.

Processing the magnetic data was quite a challenge.  To take the data we place flags along the path we walk, take their coordinates and press mark at each flag.  The instrument is collecting a magnetic reading every 1/10 of a second.  I ended up writing code that assumes a constant walking place between flags and linearly interpolates positions between.  The code then re-writes a new datafile that can be plotted by OASIS.  The quick code hack was not perfect and really should have already been in the software that came with the instrument.  Hopefully over the summer I'll have time to perfect the code and write a nice GUI to go along with it.  (Error checking would also be nice)

Finally on the last day of camp we had to give a presentation of the results.  Cullen and I talked for about 40 minutes and then there was much discussion between the faculty of our image.  We had everybody excited about what we should try next year!  Unless plans change it is likely that Cullen and I will TA next year.

Now I'm at NASA in Houston, TX.  Towards the end of this week I'll start a weekly post about the work here.  It's very exciting work with a flying vehicle and guidance software.  Stay Tuned!  Below are a few pictures from the group trip to Pike's Peak.  A copy of the final report can also be downloaded HERE.

Week 2 (Seismic Week) - Field Camp 4

This week was seismic week for us here in Canon City.  We carefully selected a site that crosses from sediment into basement, but the nature of the contact is unknown.  It ran across the property of a nice couple who moved here from Iowa three years ago.  They are interested in the geology and were more than happy to have us tramp all over with magnetic, gravity, and finally seismic gear including a larger thumper mounted on an ATV.

The first part of the week involved Cullen and I working on a mounting system to attach the thumper for the four-wheeler.  Seismic surveying works on the premise that different rocks have different wave velocities as a function of the type of rock, fluid content, etc.  We set out a long line of geophones (basically a vertical seismometer) and then hit the ground very hard to induce a signal.  From the return of the signal we can learn a lot about what the subsurface looks like.

For some surveys we hit the ground with a sledgehammer, shoot it with a gun, or even use dynamite! In this case we tried a new device that pulls a 40kg weight up with an electric motor and then drops it.  There is also a giant rubberband that accelerates the weight towards the ground.  There is currently a battle going on between naming the machine the seismic thumper device or the seismic thumper and utility device.  We added weights, battery mounts, and even a flashing safety light to the four-wheeler.

Before we could even use the thumper the control box failed due to a cable issue, so I had to rewire the control system (actually just a solenoid control) and mount the switch in a box on the ATV.  It was a midnight patch up, but it worked well all day!

The survey was laid out on Wednesday.  The line was almost 750m long, then we even rolled it forward! Geophones were placed every 10m and the thumper was shot at each geophone three times to 'stack' the data (this helps us reduce random noise).  We don't have any images yet, but tomorrow we begin processing.  The line took a day to layout, a day to shoot, and tomorrow morning to roll up.  Several long days for us here.  I also put together a quick video of the thumper shooting.

On a side note, we also took a great hike and field trip in the past week, so I've added a few photos of the Collegiate Peaks, and Tunnel Drive Trail.

Week 1 - Field Camp 3

Week 1 has been very busy and week 2 is almost to begin.  We were lucky with the weather, but this week looks to begin the inevitable warm up that we all knew would come.  This week the geophysics group went on a field trip to get the regional setting (Monday), learned detailed surveying with the TOPCON differential GPS (Tuesday), conducted a gravity survey, and a magnetic survey (days dependent on group assignment).  The week ended on Saturday with another field trip out west to see some different formations.

The regional field trip went well and we scrambled across some slopes to see most of the section that the geologists would be mapping and be very familiar with.  As a geophysics student I was more interested in the rock properties, what methods we could differentiate them with, etc.  This trip did help put things in a big picture geologic perspective though.

The differential GPS surveying went well despite a few equipment setup issues, which were to be expected with new users.  The basic premise of the system is to leave a very precise GPS unit in place all day while another identical unit is used as a rover.  The two data sets can then be merged using the base to correct for signal attenuation by the continually changing atmosphere and other error sources.  In general sub-centimeter accuracy is achievable.  This accuracy in elevation is especially important in gravity data processing since 1m makes .3086 mGal difference in the data.  While some complain that taking 2 minutes to get a GPS fix is unreasonable I remind you that we are getting a very accurate position on an irregularly shaped rotating planet FROM SPACE... it's amazing it dosen't take longer.

The gravity survey looks at density differences in the subsurface while the magnetic survey examines differences in magnetic susceptibility.  We are interested in contracts between sediments and basement or with a dike especially in this area.  After the processing I will post some results, but I know the magnetometer went crazy when I passed over the suspected location of a large dike.  The gravity survey should also be helpful, but the gravimeter does instill a certain amount of fear in everyone since it is ~$100,000 and VERY easy to break.  Omar is modeling the magnetometer in this picture.

Finally, we went on another trip Saturday which involved me getting some nice rocks with chlorite in them for bookends from a tailings type pile in a field.  This week will be seismic week, so stay tuned for updates and pictures of our new (hopefully) 700m long seismic line!

Setting Up Equipment - Field Camp 2

The past few days have been working to get a solid radio link to downtown.  The internet signal comes up on a 5.8GHz link, is distributed over a 5.12GHz mesh around the camp, and is repeated to others on a 3GHz haul over the canyon.  Below is a picture of the stack at the top of the camp on the study hall.  The repeaters are mounted on the sides of cabins.  The current link is slow, but a new circuit will be installed downtown giving us a fast connection this week.  Also included is a picture of the geophysics server (named thor) and the associated gear.

We also worked on setting up the thumper.  This is a machine that attaches to a trailer hitch of any vehicle (truck, ATV, etc) and impacts the ground with a great force.  We use this in seismic imaging.  Normally we use a sledgehammer for small surveys, but that can get tiring.  For large, deep surveys explosives are used, this machine is a great middle ground.

As you can see there is still some work to be done.  Tomorrow the hitch will be modified and in the evening I'll be building some custom brackets and mounts for the controls and battery with Dr. Keranen.  We'll use aluminium angle iron to build most of the mounts, pictures will follow.

Tomorrow we all leave early for a regional trip to get the general geological/tectonic setting of the area.  This trip will be both geologists and geophysicists.