Temperature Data From Wells in Long Valley Caldera, California

The database

The database contains temperature logs obtained by private industry, the U.S. Geological Survey, and Sandia National Laboratory. Logging methods and equipment have varied between years and companies or agencies. Because of differences in the equipment or methods, the quality, resolution, and precision of the data are not the same for all the logs. For most of the logs made by private companies the precision is not known. USGS has produced temperature data using portable gear and also by geophysical logging trucks. The USGS portable temperature-measuring gear uses a hand-cranked cable reel with four-conductor wire and calibrated thermistor or platinum resistance sensors that typically provide an accuracy of 0.1°C and precision of .01°C (Sass and others, 1971). The “stop and go” method is used with the portable gear, which involves lowering the sensor on cable over a calibrated counter wheel mounted on the well head to the selected depths and waiting about 1-2 minutes until the resistance reaches a stable value, from which a temperature is calculated. Temperature data collected by the logging trucks were electronically recorded, generally while the sensor was lowered at a constant speed over the desired depth range. The USGS logging trucks and equipment that have been used from the 1970s to recently have included different configurations, but the accuracy and precision have remained better than 0.1°C and 0.01°C, respectively. The temperature data in this report are saved in comma-delimited text files (*.csv) and Excel spreadsheet files (*.xls). Each data file contains a header that indicates the name of the well, logging data, method used, and the name of the logger. The file then contains three columns: Depth (ft) – Depth (m) – Temperature (°C).

First posted September, 2010, version 1.0

Revised November 4, 2016