DATABASE OF VOLCANO SYMMETRY USING SRTM IMAGERY

The shuttle radar topography mission (SRTM) flew on the Endeavor spacecraft in 2000, creating a database of digital topographic elevation covering most of Earth. Images from the mission are publicly available at 90-meter resolution throughout the world except in polar regions and United States topography is available at 30-meter resolution. Both data sets are unfinished products publicly released by NASA.

Using ENVI 4.1 geographic image analysis software and SigmaScan Pro scientific imaging software, SRTM images of volcanoes are analyzed for maximum elevation and geographic location along with a measure of the semi-major and semi-minor axes using the color saturation function of SigmaScan. The intersection of these axes (the symmetrical center of a given volcano) is then analyzed for geographic position, elevation, and distance and direction from the maximum elevation. These metrics determine a percentage for the symmetry of the volcano from the ratio of the semi-major and semi-minor axes.

Our objective is to create a database of volcanoes worldwide to study the variance in volcano morphology as a function of volcano type and tectonic setting. For example, a comparison can be made between stratovolcanoes and shield volcanoes or active subduction and intraplate hot spot environments based on symmetry variation and distance between the maximum elevation and the intersection of the semi-major and semi-minor axes. We compare these attributes as a function of volcano type (based on Smithsonian Institute's Global Volcanism Program classification) and relative plate motion. An example of the type of data for one volcanic system is shown below:

Volcano Name: Laguna Verde (1505-096) Maximum Elevation: 5458m Lat./Lon.: -23.243, -67.712 Azimuth (Intersect-Max Elevation): 128.1 Semi-major Axis Length: 3960m Semi-minor Axis Length: 3600m Distance (Intersect-Max Elevation): 720m Elevation of Intersect: 5235m Symmetry: 90.73%

A database that includes over 100 Chilean stratovolcanoes and 150 shield volcanoes from around the world has been developed. Additionally, planetary databases for volcanoes will be added and compared to the terrestrial database to look for analogues between the volcanoes of Earth and other volcanically active bodies in the solar system to better understand volcanic processes.