Sensors

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This passive 1-Hz sensor is seldom used because there are not many in the EPIC fleet and they have essentially been replaced by the CMG-40T-1Hz feedback seismometers.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.

Salient Features:

EPIC owns two types of 40Hz vertical geophones.

The 40Hz geophones for the Multichannel Digitizer Systems are manufactured by Sercel and Geospace.  These vertical geophones are critically damped at 0.555 and have a sensitivity of about 21 V/m/s. The 40Hz geophones for the Texan Digitizers these geophones are manufactured by Sercel.  These vertical geophones are critically damped at 0.555 and have a sensitivity of 35.3 V/m/s.  The Texan Digitizer is no longer actively employed by the EPIC, but remains in storage.

Uses primarily include active source studies.

Salient Features These single component geophones are available as vertical 6-channel strings for use with the multi-channel digitizer systems.  The multi-channel strings are rarely used. This single channel vertical geophone has a frequency of 4.5Hz, damping of .707 critical and a sensitivity of 100 V/m/s. The primary use of these geophones is for active source experiments. Manufacturer Documents: EPIC’s 4.5Hz, vertical geophones were manufactured by Geospace under part number GS-11D. Installation & Troubleshooting:

 Installation requires a separate bubble level to be placed on top of the geophone for proper leveling.

Salient Features: This 3-channel sensor has a frequency of 2.0Hz, damping of 0.707 critical and sensitivity of 88V/m/s. Best used for (but not limited to) measuring local earthquakes, teleseisms, and some active source. Types of Projects include: determination of site response, determination of crustal structure, volcanic studies, aftershock studies, and glacial studies. Manufacturer Documents:

Link to Sercel seismometer page

Salient Features: Flat response to velocity from 120 seconds to about 10 Hz Low power Installation Tips: Example of STS-2/RT130 Setup One-pager field sheet

  Troubleshooting Tips: If you cannot center the masses of even one of the 3 elements of the STS-2, all your data could be compromised. The document provided here will guide you to a 'manual' process for attempting to get those masses centered, IF and ONLY IF the masses do not center after repeated (a dozen tries) centering commands.