Table of contents
    1. 1.  
          1. 1.1.1.1. Seismic stations
          2. 1.1.1.2. Seismic blasts

     

    The SAHKE II array will consist of 900 transportable single-component seismic stations that will be deployed along a single high density transect line, stretching from Glendu Rocks in the east to Paekakariki in the west and will record signals from man-made earthquakes ( < Magnitude 1). The stations will be roughly 100 m apart in most segments of the line with some densification of stations closer to known active fault zones. Fig4_map.jpg
    The data recorded at the stations will provide a large amount of information regarding the substructure of the earth in this region. The energy released by the man-made earthquake (seismic blasts) recorded at each seismic station provides seismologist with information about the rocks through which the energy travelled between the blast and the sensor. This information can be used to create a “CAT scan” like image to help locate subsurface faulting; rock boundaries; and regions of high stress.


     

    Seismic stations

    Fig3_instrument.jpg

    Transportable seismic stations, such as those being used during this survey, are small, compact, and non-intrusive. There is no noise or motion associated with the equipment. They are designed to detect and record noise and earth micro-motion. To reduce wind interference and to protect the equipment, the instruments are buried. For temporary sites like these, the instruments will be buried in a 30-50cm deep holes. The spike is inserted into the hard soil / clay at the base of the hole to ensure strong coupling with the ground. This produces better energy signal detection at the station.
     
    The recording devices only have the capability to record for 7 days, so timing will be crucial. The stations will be deployed for the complete line over 2 day. They will be left for 3-4 days to record the blasts and then collected over the next day or two. All equipment will be removed and the holes filled back up.
     

    Seismic blasts

    Land based controlled source seismic blasts provide vital information about the Earth's structure and fault line locations in the upper 20-40 km of the continental crust. They involve timed detonations of explosives at strategic locations. With both the location and time of the event known, accurate seismic velocity models can be produced allowing more precise locations of earthquake epicenters to be estimated.

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