Sensors

All poles and zeroes in radians/sec

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.

EPIC'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.

Your choice of seismic sensor for Polar research will depend on your scientific targets. EPIC has a wide range of both passive and active seismic sensors appropriate for controlled source, local or regional seismicity, ice dynamics or teleseismic studies. A comparison of our sensors can be found here.

Short Period Sensors

These are typically used for controlled source experiments, short term, local seismicity or ice studies.  The instruments available are the Sercel L-28 and L-22.  The L-28 is a 4.5Hz 3 component geophone while the L-22 is a 2Hz 3 component seismometer.

  Salient Features: This 3-channel sensor has a frequency of 4.5Hz, is critically damped at .707 and has a sensitivity of 32 V/m/s. Used for (but not limited to) active source (land and off-shore excitations), glacial movements, local earthquake and aftershock studies. Manufacturer Website: http://www.geospace.com/ EPIC Documents: Connector wiring information here Installation & Troubleshooting Documents: Y-28 Orientation and Installation Tips here One-pager field sheet

Sensor Manufacturer Power Corner
Frequency Damping Sensitivity Poles and Zeroes               STS-2 Streckeisen 30 ma @ 12vdc 0.0083 Hz 0.707 critical 1500 v/m/s *Depends on generation:

EPIC Intermediate-Period Sensors: Nanometrics Trillium40 Features:

The low-period corner is 40 seconds for the Nanometrics sensor. All are 3-component feedback sensors. The Trillium40 masses do not lock. One should still ship and handle them with care so as not to damage them. 

Historically, the ESP's were among the first feedback sensors purchased for the EPIC program, along with STS-2's. For that reason, the ESP's have been 'categorized' as broadband sensors when broadband stations are scheduled for EPIC experiments. The ESP's are an ever-decreasing percentage of the EPIC broadband pool and we attempt to assign them as evenly as possible, roughly 10% of the sensors for a broadband experiment from 2006 onward, and that number should decrease further after 2009.

PASSCAL Short-period Sensors: Sercel  L-22 Features:

Short-period sensors are rugged three-component seismometers that cover the frequency band from 1 Hz to 100 Hz. These sensors are used in both passive and active-source experiments. PASSCAL's short-period sensors can be either feedback seismometers requiring power or conventional, passive seismometers requiring no external power.

EPIC Passive High-Frequency Sensors: 4.5 Hz 3-channel geophones (Sercel L-28-3D or GeoSpace Y-28/GS-11-3D) 4.5 Hz vertical geophones for Multi-Channel Digitizers 40 Hz vertical geophones for Multi-Channel Digitizers See also All-In-One Systems (Fairfield Nodes, SmartSolo) Features:

Teledyne Geotech S-13 Short Period Sensor

This passive 1-Hz sensor is seldom used because there are not many in the EPIC fleet and they have essentially been replaced by the CMG-40T-1Hz feedback seismometers. Information about S-13's from the old website can be found here.

The S-13's are heavy and awkward. The three components are separate units (about 20lbs each). They have strong magnets (passive seismometers), so they require about 12-inch spacing between each component.

Mark Products L-4C

 EPIC has very few of these 1-Hz passive seismometers, and does not have plans to replace parts that fail. Thus, they are likely to be discontinued, as they are cannabalized for spare parts and lost to attrition. Information from the old website can be found here and the cable drawings can be found here.