EPIC’s current inventory of multi-channel dataloggers, which now serves as our primary system for active source surveys using geophones, is centered around the ES-3000 Geode and a 60 Channel Strata View NZXP.  The ES-3000 offers reliable performance, portability, and compatibility with EPIC’s existing multi-channel cable systems, originally designed for earlier Geometrics models.

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.

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.

Introduction:

The construction of the vault for broadband seismometers has a direct impact on the data quality. The principle of broadband sensor vault design is to minimize temperature changes, and to distance the sensor pad from the surficial layer which tilts due to temperature, precipitation, solar insolation, wind, etc.

Nearby sources of ground noise, like footsteps or acoustic noise, are reduced by shallow burial (2-5 ft.) The construction must be adapted to the site and materials available. A decision will have to be made to balance the cost and labor of different vault designs against the length of deployment, resources available, and quality of data expected.

Finding a pre-existing enclosure is a tremendous savings in time and effort. This might include missile silos, power stations, abandoned mines, caves, or root cellars. Consider the details of cables, power, and locating a GPS antenna for timing at these sites.