Passive seismic test site installed

The design for the passive seismic stations is based on the experience of Geoff Abers in Alaska.  The details of that design are shown in the following description and photos. A hole is cut in the bottom of a large plastic trash can and a hole dug of an appropriate size to just have the top of the garbage can above the ground surface.


A small concrete pad is poured in the bottom of the can on which the seismometer is placed and gravel is poured around the pad.


After connecting the seismometer cables a smaller plastic can is inverted over the seismometer and weighted and tied down to anchors under the pad.  If water gets into the vault it should drain out through the gravel but if it rises in the vault the air traped under the interior plastic can should prevent the seismometer from flooding. Cables are routed to the surface through a PVC pipe extending from the bottom of the vault.


Once connected and seccured a lid is placed on the vault, dirt back-filled around it, a tarp placed over it and dirt piled on top to help with insulation.  Cables extend to a nearby electronics enclosure containing the datalogger, power and timing system.