|(Seismic Petrophysics: Observation & Theory)|
High-quality broadband earthquake seismographs are now available that can be used for teaching and research purposes by interested Middle and High School teachers, right in their own classrooms, bringing geophysics to life for the students. The Houghton (MI) Middle School has constructed a dedicated pier for permanent placement of a dedicated seismograph, while other units (purchased through a grant from SEG) are deployed for 2-3 months at a time in other schools throughout Michigan's rural Upper Peninsula. The involvement of the students in recording and interpreting earthquake waves on a machine sitting in their own classroom, and the visit of a local "expert" to help in interpretation, stimulates interest in global geology, geophysics, and seismology in particular. We are currently in the process of developing and testing a new set of software that is much more user-friendly than the original version, and that should make teacher and volunteer involvement very easy. This new effort is supported by a grant from the Society of Exploration Geophysicists.
Stimulated by projects designed to establish permanent, research-quality seismograph stations in K-12 schools throughout Michigan and the rest of the US (primarily the MichSeis program of Larry Ruff at the University of Michigan, and the PEPP program of Guust Nolet and Bob Phinney at Princeton University), in 1995 we acquired a broad-band seismograph station based on a sensor costing less than $1500 and a Macintosh computer with an analog-digital converter board. This system has been located in schools in several towns throughout the rural regions of Michigan's Upper Peninsula, generally for 2-3 months at a time, recording earthquakes from around the world, right in a classroom in the school. This program is different from others, in that it does not require the school to make the investment in time, space, and money that a permanent and dedicated seismograph would require.
A recent grant provided from the SEG Foundation has permitted the purchase of three more seismograph stations, so that multiple deployments may take place simultaneously, and the requests from schools to participate in this program are not significantly delayed. In addition, a construction project expanding the Houghton (MI) Middle School provided an opportunity to build a dedicated pier attached to bedrock (PreCambrian basalts) and de-coupled from the building's foundation; a dedicated system is now installed at that site permanently, providing a "base" station for network studies. This station will likely become the best, even for research, for hundreds of miles in any direction. The other systems will continue to be deployed temporarily in schools throughout the area.
How Our Program Typically Works
We call our program UPSeis ( for Upper Peninsula Seismic experiments in schools), and are continually expanding its reach, including providing a dedicated web site (through www.geo.mtu.edu). In general, the operation has followed this scenario:
* A teacher or principal learns of the UPSeis program through word-of-mouth or public presentation, and contacts us.
* We establish a date for installation of the seismograph of the equipment in the teacher's main classroom (usually an Earth Science class, but it could be anywhere). The only requirement is that the sensor can be placed on the floor, out of heavy foot traffic; it is usually off to the side in the front of the room.
* On the scheduled day, the first author of this paper (and sometimes interested graduate and undergraduate students) drives to the school (sometimes many hours away), and sets up the sensor and recording computer before the first class. The Macintosh computer is placed on a table in full view of the class at all times.
* We then present an introduction to the recording system, various web sites (for the identification of recent earthquakes) and a general discussion of the nature of earthquakes and seismograms to each class throughout the day. Typically, this involves remaining at the school all day, and repeating the introduction several times. The interest level of the students is usually very high.
* The seismograph equipment is left installed for two to three months, usually long enough to record at least three or four large earthquakes from around the world. When one of these occurs during the day, the class is often disrupted by the excitement of seeing the large waves playing across the computer monitor. We have never heard a teacher complain about the clamor it causes - they are usually grateful to see the students become engaged with the discovery process.
* The location, magnitude, and other information about large earthquakes is readily available on the internet shortly after their occurrence (a good site is the IRIS Monitor available at www.iris.edu) and the teacher and students can soon learn what it is they've recorded.
* After enough earthquakes have been recorded, and the seismograms sent (via floppy disk or e-mail) to MTU, we prepare a set of seismograms and travel-time tables based on those earthquakes, and return to the school for another complete day or more of interaction with the classes.
What the Students Learn
During our second visit to the school, the students are each provided with a copy of each major earthquake seismogram (see Figure 1 for an example), a list of all large earthquakes that occurred during the time period that the seismograph was deployed, and a set of travel-time tables. The students first must identify each recorded earthquake from the list provided; they are quickly amazed at the fact that Universal Time is actually useful for some purpose, and at how many earthquakes typically occur on any day. It is not enough to simply identify the date; in fact, they often need to realize that the seismic waves will not arrive at "their" station until some time after the earthquake has occurred, to allow for travel time through the earth. They then locate the earthquakes, one at a time, on a globe (we usually find that the globes in most schools are miserably out of date and in bad shape - the resulting embarrassment of the school officials often instigates the wholesale purchase of new globes before the next year!), using string (a "high-tech scientific measuring device") to find the distance from the epicenter to the recording station.
In order to find the distance to the earthquake, the students first have to locate the earthquake on the globe, and most of them, of course, have no idea where to find the Kermadec islands, or Vanuatu (particularly if the globes are old). So they must resort to using latitude and longitude to find these locations on the globe, usually for the first time for a "real" application. The teacher has been informed in advance that this will come up, and he or she has already adjusted the syllabus, if necessary, to be sure that these skills are taught before the earthquakes are reviewed. The interaction between teams of students working on these aspects of interpretation and the visiting professor and students is a key to the success of the exercise; many students respond very well to the interest exhibited in their success by the guest teachers.
The students then use the distance they find from the string and globe together with a set of travel-time curves, with phases that we know to be important in their seismograms highlighted. The complexity of the sequence of operations is generally more than most students have ever been expected to perform in school prior to this exercise. Even with an outline of the operations written on the board, they find the fact that they need the results from one step before continuing on to the next to be challenging, in many cases; and the sense of satisfaction once they have completed it all is genuine.
Often, the students are using skills that they have (more-or-less) learned in various classes in order to learn something new, for the first time. Whether it is locating a point on the globe (in order to find it, rather than in order to answer an assigned problem); obtaining a value from a graph (which was never more than an academic exercise to them in the past); or putting together information from a table, a globe, a graph, and their knowledge in order to understand something new - each step seems to be a new revelation, and the synthesis of data and observations certainly is.
It is not clear that students would respond as well if we simply provided seismograms and other information without having the equipment operating in their room before the interpretation exercise. In fact, it is likely that the sense of ownership ("That earthquake was recorded in my classroom and I saw it being recorded!") plays an important role in obtaining the students' cooperation for a genuinely complicated interpretation sequence.
The UPSeis experience has been a good one, and we hope that it will continue to expand, so that all the seismographs are busy during the entire school year. We would like to encourage other professionals or groups with the economic resources to support operation of portable seismograph stations to consider emulating our efforts, and to improve on them.
We would like to thank the SEG Foundation for support of equipment purchase, the Houghton-Portage Township Schools for construction of the seismic pier, and the many teachers and principals who have encouraged our work. The software we are currently using was written by Dr. Larry Ruff of the University of Michigan - Ann Arbor, and his encouragement and assistance has been extremely valuable.