In October 2021, GFZ installed together with INGV Catania, Iraci and ASIR Ltd (Advances Seismic Instrumentation & Research) the very first seismic borehole broadband seismometers at two selected sites at Mt. Etna, Sicily (see Fig. 1). The installation was completed under the EU-funded project ‘SiC nano for PicoGeo’ (http://www.picogeo.eu/). Site one is located next to the Astrophysical Observatory at Serra La Nave (SLN) and site two is located in the city of Mascalucia (MAS). At each site one borehole broadband seismometer was permanently installed (cemented) at approximately 70 m depth. In approx. 1-2m distance, a second ground-level borehole 4.5 Hz Geophone was temporarily installed (sanded) at 1 m depth until July 2022 (see Fig. 2). The ground-level geophones served as a local surface reference sensor to better evaluate the increase of signal quality from surface to depth. Test data were evaluated between October 2021 and July 2022. Sensor settings were adjusted during this time period to obtain the best possible data resolution at both test sites. This data publication compiles a segment of waveform recordings utilized for the assessment of data quality from the two installed broadband borehole seismometers, along with noise plots (Fig. 3-5) illustrating the enhancements in the data quality of frequency ranges compared to surface sensors at Mt. Etna.
GEOFON (GEOFOrschungsNetz) is the global seismological broad-band network operated by the German GeoForschungsZentrum (GFZ). The GEOFON seismic network came into being in 1993 as one of the three pillars of the GEOFON program dedicated to Ernst von Rebeur-Paschwitz, proposer of a global earthquake monitoring system, who recorded the first teleseismic seismogram in Potsdam in 1889. The program and its seismic network were created to provide high quality broad-band data for scientific use and foster common standards in the seismological community. The network has evolved towards real-time data acquisition and distribution while keeping the high quality broad-band data in focus. Today the network plays a leading role in global real-time seismology providing valuable data for almost all fundamental and applied global/regional seismological research projects at GFZ and the wider seismological community.
The GEOFON network is operated jointly with more than 50 international partners and in 2014 consists of about 80 active stations on all continents, but concentrated in Europe and the Mediterranean region as well as in the Indian Ocean. Station operation is mostly performed by local partners with GFZ guidance and logistic support, allowing the global network to be well-advanced technically while still extremely cost-effective. All stations are equipped with broad-band sensors (generally STS-2) that allow resolution of the complete seismic spectrum from small high-frequency local earthquakes to the largest global earthquakes.
Data from all stations are freely redistributed in real-time for earthquake monitoring and tsunami warning centers immediately after acquisition at the GEOFON data centre via wired or satellite links. Archived data is also available. GEOFON is part of the Modular Earth Science Infrastructure (MESI) housed at GFZ.