@article{vanWijk:5033,
      author        = "van Wijk, Kasper and Chamberlain, Callum J and Lecocq,
                       Thomas and Van Noten, Koen",
      title         = "{Seismic monitoring of the Auckland Volcanic Field during
                       New Zealand's COVID-19 lock-down}",
      year          = "2021",
      note          = "The city of Auckland, New Zealand (Tāmaki Makaurau,
                       Aotearoa), sits on top of an active volcanic field. Seismic
                       stations in and around the city monitor activity of the
                       Auckland Volcanic Field (AVF) and provide data to image its
                       subsurface. The seismic sensors – some positioned at the
                       surface and others in boreholes – are generally noisier
                       during the day than during nighttime. For most stations,
                       weekdays are noisier than weekends, proving human activity
                       contributes to recordings of seismic noise, even on
                       seismographs as deep as 384 m below the surface and as
                       far as 15 km from Auckland's Central Business District.
                       Lockdown measures in New Zealand to battle the spread of
                       COVID-19 allow us to separate sources of seismic energy and
                       evaluate both the quality of the monitoring network and the
                       level of local seismicity. A matched-filtering scheme based
                       on template matching with known earthquakes improved the
                       existing catalogue of five known local earthquakes to 35
                       for the period between 1 November 2019 and 15 June 2020.
                       However, the Level-4 lockdown from 25 March to 27 April –
                       with its drop in anthropogenic seismic noise above 1 Hz
                       – did not mark an enhanced detection level. Nevertheless,
                       it may be that wind and ocean swell mask the presence of
                       weak local seismicity, particularly near surface-mounted
                       seismographs in the Hauraki Gulf that show much higher
                       levels of noise than the rest of the local network.",
}