Methodology:

Event locations were gained from the continuous passive seismic records using the QuakeMigrate (Hudson et al., 2019; J. D. Smith et al., 2020) and Nonlinloc (Lomax et al., 2000) software. A two-layer velocity model (firn layer above an ice layer) according to E. C. Smith et al. (2015) was used in the Nonlinloc location step. Based on Nonlinloc locations, we accept only events with a total root-mean-square (RMS) value of 0.02 s, a maximum azimuthal gap of 280 degrees, maximum 10% of picks with a P/S residual larger than 0.02 s/0.2 s and at least 3 P picks and 2 S picks for the final event catalogue.

We account for the movement of the seismic stations relative to the bed due to ice flow by shifting each event in the final catalogue downstream. Rutford Ice Stream moved ~94 m downstream during the 90 day survey period, whereas our stations are specified at fixed locations during event location, clearly evidencing the necessity for such a shift. We perform this shift by calculating the stations' locations at the time of each individual event relative to the start of the deployment, using their GPS locations, and apply this lateral shift to that event hypocenter. This is repeated for all events in the catalogue to compensate for ice flow.

Magnitudes were calculated from the far-field displacement of the P-wave (Mw; Shearer (2009); implementation of Hudson (2019)) for a 1-day data subset. A local magnitude scale (ML) was then derived based on these Mw values. The local magnitude scale follows the equation:

ML = log10(A) + m x depi - t

where A is the maximum amplitude of either of the two horizontal components (in instrument counts corrected for the instrument type). The distance term m accounts for the decay of amplitudes with increasing epicentral distance, depi is the epicentral distance and t is a scaling parameter that bridges the offset between Mw and ML.

Focal mechanisms were calculated from first motion polarities and P to S- amplitude ratios using the HASH software (Hardebeck & Shearer, 2002, 2003). The final set of good solutions is derived based on quality criteria, which are the stability of solution upon variations of input, the azimuthal gap of the final set of stations (should be smaller than 180 degrees) used and the final number of input picks (should be larger than seven).

Detailed information on catalogue creation will be contained in Kufner et al. (in prep.).

Data collection:

Instrumentation:

Each station of the seismic network consisted of a Reftek RT-130 data logger with a 4.5 Hz 3-component geophone (either GS11-3D or L28-3D), which was buried to ~1 m depth. The sampling frequency was set to 1000 Hz. Energy supply was ensured through a solar panel and batteries. Timing was obtained from an attached GPS antenna.

Software:

Event detection from continuous data: QuakeMigrate (https://github.com/QuakeMigrate/QuakeMigrate); October 2019-Version

Event relocation: Nonlinloc (http://alomax.free.fr/nlloc/); Version 4, including updates until 2017

First motion focal mechanisms: HASH (https://www.usgs.gov/software/hash-12); Version 1.2, January 2008

Data quality:

See Lineage for quality restrictions applied to the event hypocenters and focal mechanisms. Location errors are given directly in the data file.