DOI: 10.5066/p9310m9n
title: Tiltmeter data from Kilauea Volcano, Hawaii, spanning the 2018 eruption and earthquake sequence.

description: Data collected by 11 borehole tiltmeters operated by the U.S. Geological Survey on Kilauea Volcano, on the Island of Hawai'i. Data was collected between 30 April, 2018 and 5 August, 2018. Among the features captured by this data set are: the collapse of Puu Oo on 30 April, 2018, the migration of magma down the East Rift Zone from 30 April to 3 May, 2018, the M6.9 earthquake on 4 May, 2018, and the deflation and collapse of the shallow magma chamber at Kilauea from early May until 5 August, 2018. Data files for each station are zipped together into a single archive, which also includes a ReadMe.txt explanatory file. Zip archives are named with the three-letter station code that uniquely identifies the tiltmeter instrument and with the tiltmeter type; tiltmeter type is either &amp;iuml;&amp;iquest;&amp;frac12;analog&amp;iuml;&amp;iquest;&amp;frac12; or &amp;iuml;&amp;iquest;&amp;frac12;digital&amp;iuml;&amp;iquest;&amp;frac12; (for example, UWD_digital.zip) Inside each archive is a comma separated value (CSV) file containing the data. Data files are named with the station name, the start and end times of data contained within them, and the tiltmeter type. Start and end times are formatted as YYYYMMDDTHHMMSS, and are given in UTC (for example, UWD_20180430T000000-20180520T193000_digital.csv). Any missing data from within the timespan indicated in the file name, if not contained in the file, was not collected (for example, station outage). Note that positive values for east-directed tilts correspond with tilting down to the east. Negative values in east-directed tilts indicate tilting down to the west. Similarly, positive north-directed tilts are tilting down to the north and negative values indicate tilting down to the south. Multiple CSV files are generated when there is a loss in continuity in the time series (in other words, a data tear). The most common reason for this to happen was that the tilt sensor reached its physical limit (typically around 300-330 microradians) and the instrument needed to be releveled. This would then return the tilt value back to around zero. Each archive also contains an additional descriptive text file (for example, UWD_Readme.txt) that contains station-specific metadata including latitude/longitude, the values of constants used in data conversion, and descriptive comments. Station metadata are also summarized in the file KilaueaTiltmeterMetadataDigest.csv, but this file should not be used as a replacement for reading the individual station ReadMe.txt files. Tiltmeters are generally susceptible to long-term drift. This effect is strongly noticeable at station Sandhill (SDH); check this station's ReadMe.txt file for information on this instrument's long-term drift. All other tiltmeters may also experience some amount of long-term drift, but the rates are small enough that they become difficult to separate from deformation signals. All of the tiltmeters, except UWD, sampled at a rate of 1 data point per minute throughout the eruption. Tiltmeter UWD sampled at 1 point per minute until 5/20/2018, at which point it was reprogrammed to sample at 1 point per second. Two sets of files are available for UWD. Files with 1-second data are marked &amp;iuml;&amp;iquest;&amp;frac12;1sec&amp;iuml;&amp;iquest;&amp;frac12; (for example, UWD_20180520T193000-20180702T040400_digital_1sec.csv). Files containing data decimated to 1 point per minute are also provided; for example, UWD_20180520T193000-20180702T040400_digital.csv is decimated from the 1-second data. Decimation was accomplished by taking the median of all on-scale, 1-second samples from the previous 60 seconds. Decimated records were generated only for the 1-minute periods containing at least 10 on-scale 1-second samples. The timestamp of each data sample marks the end of the period over which the sample was generated. For digital tiltmeters, the sample is taken by averaging through 40 seconds of data. For analog tiltmeters, the accompanying datalogger averages through 60 seconds of subsamples to generate the data point. 1-second samples at station UWD, are generated by averaging through the previous second. The clocks on the digital tiltmeters and dataloggers attached to the analog instruments drift by up to several seconds per day. Estimates of clock drift are given in the station ReadMe.txt files, as well as times when the clocks were reset. Tilt values obtained from the tiltmeter are assigned the name Xtilt and Ytilt, and are later converted to true east (EastTilt) and north (NorthTilt) using the following conversion equation: EastTilt = (cos(Az)*cX*Xtilt)+(sin(Az)*cY*Ytilt) NorthTilt = (-sin(Az)*cX*Xtilt)+(cos(Az)*cY*Ytilt) Where cX and cY are conversion constants and Az is the azimuth direction of the instrument&amp;iuml;&amp;iquest;&amp;frac12;s Y component. Instrument azimuths are measured by hand using a Brunton compass and are presumed to be good to +/- 3 degrees.