Presentation Title

Measuring Deformation of the Resurgent Dome within the Long Valley Caldera, Central California

Faculty Mentor

Jascha Polet

Start Date

18-11-2017 9:59 AM

End Date

18-11-2017 11:00 AM

Location

BSC-Ursa Minor 144

Session

Poster 1

Type of Presentation

Poster

Subject Area

physical_mathematical_sciences

Abstract

Measurements of ground tilt and deformation within Long Valley Caldera in Central California provide important insight into the continued upward push of the resurgent dome due to pressure by magmatic intrusion. In the early 1980’s, after a series of earthquakes and volcanic unrest, a network of nine dry tilt arrays was established around the dome to monitor inflation. Each array consists of a primary and a secondary set of three permanent benchmarks placed in an equilateral triangle with side lengths of about 35 to 40 meters. Over the course of a geophysics class in July 2017, students re-measured three arrays: Convict Lake, Hot Creek Gorge, and Escape Route. For all three sites, two Total Stations and one Real Time Kinematic GPS unit were used to carry out high precision elevation measurements.

We compared elevation differences between monuments for the 2017 measurements with those from Dzurisin et al. (1982) and Sylvester (1985). Trends in changes in elevation differences between monuments indicate mostly consistent deformation. Calculations of tilt, in microradians, and azimuth from these differential elevation changes reveal a consistent tilt direction over the past 35 years as compared to Sylvester’s findings in 1985, based on only three years of data. Hot Creek and Convicts Lake’s eastwards tilt persisted, while Escape Route’s tilt continued southwest. This July’s results, however, show a significantly larger tilt, as expected given the longer time period. Continued upward movement of the resurgent dome, with an asymmetry towards larger tilt on its eastern side, is a likely explanation.

Keywords: Deformation, tilt, volcano, geodesy, geophysics

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Nov 18th, 9:59 AM Nov 18th, 11:00 AM

Measuring Deformation of the Resurgent Dome within the Long Valley Caldera, Central California

BSC-Ursa Minor 144

Measurements of ground tilt and deformation within Long Valley Caldera in Central California provide important insight into the continued upward push of the resurgent dome due to pressure by magmatic intrusion. In the early 1980’s, after a series of earthquakes and volcanic unrest, a network of nine dry tilt arrays was established around the dome to monitor inflation. Each array consists of a primary and a secondary set of three permanent benchmarks placed in an equilateral triangle with side lengths of about 35 to 40 meters. Over the course of a geophysics class in July 2017, students re-measured three arrays: Convict Lake, Hot Creek Gorge, and Escape Route. For all three sites, two Total Stations and one Real Time Kinematic GPS unit were used to carry out high precision elevation measurements.

We compared elevation differences between monuments for the 2017 measurements with those from Dzurisin et al. (1982) and Sylvester (1985). Trends in changes in elevation differences between monuments indicate mostly consistent deformation. Calculations of tilt, in microradians, and azimuth from these differential elevation changes reveal a consistent tilt direction over the past 35 years as compared to Sylvester’s findings in 1985, based on only three years of data. Hot Creek and Convicts Lake’s eastwards tilt persisted, while Escape Route’s tilt continued southwest. This July’s results, however, show a significantly larger tilt, as expected given the longer time period. Continued upward movement of the resurgent dome, with an asymmetry towards larger tilt on its eastern side, is a likely explanation.

Keywords: Deformation, tilt, volcano, geodesy, geophysics