EARTHQUAKES AND PLATE BOUNDARIES: A MODEL EARTHINQUIRY ACTIVITY

EarthInquiry activities are being developed by the American Geological Institute, along with geoscience instructors. They are designed to help introductory college students interact with the abundant real-time and archived geoscience data available on-line. Each activity has its own workbook, printed by W.H. Freeman and Company Publishers, that contains a web-access code, allowing students entry into the EarthInquiry web site. The EarthInquiry web site, maintained by AGI, provides students with detailed instructions on how to access and interpret the data collected in each activity. The web site also supplies supplementary information, glossary terms, and, in some cases, web-based tools to assist with numerical manipulation.

In the Earthquakes and Plate Boundaries activity, students first learn about earthquakes as natural hazards, in terms of their cost, magnitude and global distribution. This understanding is established using short media excerpts and historical statistics. Students are then introduced to the USGS National Earthquake Information Center database. An "Earthquake Orientation" encourages students to look at recent worldwide earthquake activity. To become more comfortable with how earthquake data is recorded and displayed, students look at the extremes in earthquake depth and magnitude over the past week. They also consider how earthquake distribution largely coincides with plate boundaries. Following a brief summary of the different types of plate boundaries, the students once again access the NEIC data to examine a seismic cross-section in western South America. Using trends in hypocenter depth, an on-line plotting utility, and an "angle calculator," students quantify the angular relationship that exists along the cross-section and develop an understanding of how earthquake distribution can be used to express the geometric relationship between Earth's plates

The focus of the activity then shifts north to the San Andreas Fault in California. Students compare and contrast the earthquake distribution observed in California to the distribution observed in South America. Finally, students investigate predicting earthquake hazards using spatial and temporal patterns in earthquake distribution. The Loma Prieta event (1989) is used to help demonstrate this concept.