Redefining Earthquakes and the Earthquake Machine: Students Use the Earthquake Machine Lite to Refine Their Ideas about the Causes of Earthquakes

[ILLUSTRATION OMITTED] The large earthquakes off the coast of Sumatra, with magnitudes ([M.sub.w]) of 9.1 and 8.7 in 2004 and 2005, have recently brought geophysics to the forefront of the world's attention. While the awe-inspiring power of such events makes them a highly engaging topic for many Earth science students, maintaining this interest once the video footage of earthquake damage has ended can be a challenge. Further, the nature of earthquakes makes it difficult for students to collect, explore, and explain empirical data about earthquakes in the lab. The Earthquake Machine Lite (EML), a mechanical model of stick-slip fault systems, can increase student engagement and facilitate opportunities to participate in the scientific process. The model can be used to explore causes of earthquakes, distribution of event occurrence in time, distribution of event size, and earthquake prediction. This article introduces the EML model and an activity that challenges ninth-grade students' misconceptions about earthquakes. The activity emphasizes the role of models as part of the scientific enterprise and the concept of scientific inquiry as a continuing, creative process of explaining natural phenomena. Modifying the original Earthquake Machine Over the past four years, the Incorporated Research Institutions for Seismology (IRIS) professional development workshops (see "On the web," at the end of this article) have introduced teachers to the Earthquake Machine. This model uses a brick, six-foot-long board, bungee cord, and crank to represent the behavior of a stick-slip fault system (Hall-Wallace 1998; Ringlein 2005). Assessments of IRIS workshops where the original model was used revealed that participants enjoyed working with the model and developed professionally from the experience, but follow-up surveys conducted one year later revealed that only 15% of workshop participants actually constructed and used the models when returning to their classrooms (Hubenthal, Braile, and Taber 2003). While this original Earthquake Machine provides an accurate, concrete representation of the abstract phenomenon of earthquake generation, it seems possible that the cumbersome size, cost, and complicated construction makes it accessible for only the most enthusiastic of Earth science or physics teachers. Additionally, previous descriptions of the Earthquake Machine have lacked fully developed exercises or lesson plans to support teachers' use of the model with students. This means that if teachers want to use the original model with students, they need to develop their own activities. Given their limited experience with the model and the background content knowledge required to design such exercises, many teachers from the workshop may have simply determined that the effort was too great and abandoned its use. This is unfortunate, as the Earthquake Machine has tremendous potential to help students develop deeper understanding of the nature of earthquakes. To resolve this, we have created a simple, scaled version of the original Earthquake Machine, resulting in a scientifically comparable model. The EML version is significantly less expensive, can be assembled by students, and can be packed as a class set in one large shoebox (Figure 1, p. 34). To support this new design, a series of activities have been designed around interesting questions that can be explored using the model. In keeping with the recommendations of Hall-Wallace (1998), these questions are broken into small hierarchical segments to enhance concept development for students and to highlight the strengths and weaknesses of the model. Significant opportunities for discussion and analysis of both the process and results of each exercise are also included. The activity described in this article will help you and your students begin using the EML. A materials list and instructions for constructing the model are available online (see "On the web"). …