| Summary: | Progress Code: completed Statement: The magnitude of the vibrations at the site were initially unknown, and a wide dynamic range was considered for the z-component only. After data analysis, it looks like the records with the largest amplification (i.e., signal z3) provides useful data. We note that the spurious frequency of the geophone is 240 Hz. Though signals were recorded at 1000Hz, we do not expect of the data above 240Hz to be reliable. Instruments were sometimes moved during the field experiment and redeployed due to changing ice-conditions and empty batteries. Users are advised to monitor the GPS coordinates. Data was obtained from 31-Aug-2021 to 10-Oct-2021. The experiment consists of 3x Geophone loggers deployed on landfast ice just north of Casey station. Geophone loggers record vibrations using a tri-axis GS-ONE geophone. The tri-axis geophone was dug slightly in the top layer of the ice (few centimeters), and the hole was filled with a mixture of snow and fresh water to create a slush for rapid refreezing. The geophone converts motion of a mass suspended by a spring to a voltage. The voltage is proportional to the velocity of the mass' motion. The GS-One has a (open-circuit) sensitivity of 85.8 V/m/s (+- 3.5%) and a corner frequency of 10Hz. Spurious frequency is 240 Hz. The geophone will still respond to vibrations of frequencies <10 Hz, but is simply less sensitive (see Page 2 of the enclosed datasheet). The geophone output is 3x a voltage, corresponding to the x, y and z direction. The signals are first amplified (using an INA122). The z-signal is split and amplified in three different ways to increase the dynamic range of measurements of vertical vibrations. The following gains were used: x = gain of 5, y = gain of 5, z1 = gain of 5, z2 = gain of 50, z3 = gain of 1000. Data is recorded on a microcontroller at 1000Hz, at 12-bit resolution. GPS was used to record geographical coordinates and high accuracy time-fixes. Time-fixes are accurate at 1 millisecond to allow for cross-comparison of ...
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