Year Round

Vault Equipment Drawings Vault Double wall UV resistant polyethylene shell 2" thick indexed phenolic sensor base 3" thick polystyrene insulation Trillium 240 or Guralp T3 seismometers Detailed Drawings 3" Thick Insulation 2" Thick Indexed Phenolic Base Double Wall UV Resistant Polyethylene Shell

Station Enclosure Drawings   Large Enclosure:  Insulated Hardigg AL3434-2807 External dimensions:  37" x 37" x 37" Internal dimensions:  24" x 24" x 21" 2" thick vacuum insulation panel (VIP) sub-enclosure Protective polypropylene barrier between VIPs and electronics Integrated cable harness with external bulkhead connectors Year round operation with rechargeable AGM batteries   Detailed Drawings Hardigg AL3434-2807 Insulated:  Assembly Drawing with BOM

PASSCAL's strategy for designing cold-hardened seismic systems is driven by the need to maximize heat efficiency and minimize payload while maintaining continuous recording throughout the Polar winter. Our design is for a basic 2W autonomous system. Power is provided by a primary Lithium Thionyl Chloride battery pack and is backed by a secondary, solar charged AGM battery pack. Station enclosures are heavily insulated and rely on instrument generated heat to keep the dataloggers within operating specification. Although insulated, broadband sensors are operated close to ambient temperature.

This checklist is a list of items to consider while preparing for a new field project.  It is aimed at providing a list of things to think about while making preparations for and assessments of possible seismic sites. This checklist is also appropriate for the initial installations and for the removal of the equipment at the end of the project. These guidelines are fairly general but focused for polar regions.  It applies more to the Arctic and Sub-arctic regions rather than Antarctica, because for Antarctic projects, a lot of these issues are dealt with by the US Antarctic Program.

  

Site Assessment: Climatic conditions:Wind, snow, temperature, altitude, ... Access: On foot: conditions (all year, seasonal), roughness of terrain, safety, man power, ... By wheeled/tracked vehicle: conditions (all year, seasonal), roughness of terrain, ... By fixed wings aircraft: airstrip conditions (all year, seasonal), typical weather conditions,cost, availability, safety, permitting, ... By helicopter: landing zone conditions, typical weather conditions, cost, availability, safety, permitting, ... By boat:land base vs. ship base, ease of access to land, protection from storms, issues of accidental introductions of rats and other non-native species to protected islands, cost, availability, safety, ... Permitting (Public land, private land, restricted land, fees, monitored access, limited access to certain dates, etc). Type of ground: Rock, mud, snow, ice, vegetation, sand, gravel, etc. Hazards to the equipment: Wildlife: Bears (very destructive!), rodents, foxes, cows, etc. Humans: Theft, vandalism, etc. Hazards to crew personnel: Climatic conditions. Access (steepness of terrain, crevasses, isolation, volcanic area, etc). Wildlife (Bears, moose, etc). Humans (locals with guns, etc). Site Installation: Dates: Choice of dates to simplify logistics and installation. Take into account climatic conditions. Personnel, transport and equipment availability. Maximize data return. Minimize cost. Permitting: For land use. For access. For use of vehicle or aircrafts Transport: Personnel:customs issues, ... Equipment:customs issues, potential HazMat, ... Housing: Food: Contingencies:Things rarely all go as planned. Site Removal and Equipment Regrograde: Permitting:land reclamation requirements. Transport:Methods, customs issues, potential HazMat, scheduling. Returning equipment to PASSCAL Instrument Center:

Seismic Sensor Vaults

The type of seismic sensor vault and the amount of sophistication it requires, is dependent on the type of seismometer.  A geophone does not require a “vault” per se, it can be buried in dirt or snow and be kept reasonably level in the process. A sensitive broadband seismometer requires a quiet, temperature stable and level vault.  In the Antarctic two main styles of vaults are used for broadband seismometers:  the rock vault and the snow vault.

The Rock Vault

In rocky environments where digging is nearly impossible, a weatherproof enclosure with a rigid bottom, typically aluminium, is secured to the ground.  The seismometer is then set inside, oriented properly and leveled.

To reduce noise caused by wind, and to thermally stabilize the vault and protect the instrument from flying debris, a double walled dome is placed on top of the vault and anchored to the ground as well.

Cold Rated Guralp CMG-3T

The Guralp CMG-3T seismometer is a 3-axis broadband instrument that has a flat response to ground velocity between 120s and 100Hz.  It has been tested to operate down to -55C and only draws 0.3W of power.

PASSCAL's Polar program has purchased the cold-rated 3Ts (with active logic high) for broadband experiments in Antarctica.  When powered and locked, the reported mass positions will be '0'.  This does not mean that the instrument is dead or unpowered.  Once the 'unlock' command is initiated, first the lock/unlock and then the centering motors should run and finally result in meaningful mass position readouts.

The CMG-3T has a low tilt tolerance and is sensitive to temperature changes, it therefore requires a well established and well thermally isolated vault.

Quanterra Q330

To record seismic data during the extremely cold Polar nights, the IRIS PASSCAL Polar Group relies on the Quanterra Q330 digitizer due to its exceedingly low temperature tolerance.   The Q330 is a 24 bit, 3 or 6 channel digitizer. In addition to its very low temperature tolerance, its very low power consumption makes it ideal for year round experiments in the Antarctic deep field.

 

Here are several documents regarding year round equipment for Polar Projects. Batteries DAS Power Box Sensors Solar Station Enclosure Vaults

The Polar Program of IRIS/PASSCAL is dedicated to supporting with seismological research in the Arctic and Antarctic.  As opposed to traditional seismic stations installations around the world, instrumenting the Arctic or Antarctic require special consideration due to the extreme nature of the climatic conditions, temperature being the primary challenge.

Low Power Solar Panel System

This solar panel system uses three Suntech STP020S  (20W) Monocrystalline Silicon solar panels mounted in a triangle to take advantage of the 24 hours a day solar insolation.   With the combination of cold temperature and solar reflection off the snow, this system produces close to 40W worth of solar power all day long in clear conditions.  This is more than adequate for most seismic recorder configurations.

This solar panel system is also very simple and quick to install in snow.  All that is needed is to have the base of the solar system buried in two feet or more of well compacted snow.  No guying is necessary.  Only one solar cable is needed to connect to a junction box located on the post.