ESTABLISHING A PUBLICLY ACCESSIBLE GRAVITY BASE STATION IN LINCOLN, NE

Gravity surveying requires tying to a base station. There is an unofficial gravity base station located on the Lincoln airport tarmac that requires special permission to access. Two surveys conducted by the UNL Geophysics Team that utilized this base station revealed a large mismatch of 40 mGal between the measured gravity values tied to this station and the official USGS Bouguer anomalies. Due to this mismatch, and the logistical difficulty involved in accessing the only gravity base station in Lincoln, NE, a new, reliable, and easily accessible gravity base station is needed.

The objective of this project is to establish a gravity base station on the University of NE-Lincoln (UNL) campus. To do that, we need to [1] determine the best location on the UNL campus, and [2] tie the proposed gravity base station to publically-accessible, official gravity base stations in Nebraska.

To achieve our first goal, we identified several potential locations for a gravity base station. Then, we collected gravity readings at all locations over ten months in order to determine the noise level at each one. We chose the best location by analyzing the collected data and the accessibility of the location (due to the Covid-19 pandemic, the accessibility of the proposed locations was prioritized over the noise levels). To reach our second goal, we identified several official gravity base stations within reasonable driving distance (the full loop should be completed within one day), and we performed several trips to those base stations to transfer the readings to the newly established one on the UNL City Campus.

We will present our determined value of the absolute gravity at the newly established base station and report on the estimated error based on several publicly accessible gravity stations. This base station will be used in upcoming gravity surveys in Nebraska to study the faults related to the Midcontinent rift.