Miniature Seismic Recorder Model 125A (Texan)

Miniature Seismic Recorder Model 125A (Texan) - Introduction

The REF TEK 125A Miniature Seismic Recorder “Texan” is an important advancement in the seismology industry. The Texan’s self-contained, compact design allows greater flexibility and the ability to easily integrate into system operations.

In crustal scale refraction experiments, hundreds of instruments are deployed over several hundred kilometers for two to four days duration. Recordings are made based on pre-set time windows at a rate of 100 samples per second (sps). Because explosions are typically being recorded, a maximum of 50 time windows of 120-second duration will also be recorded. The Texan’s data storage requirement for this application is about 2 MB. Timing accuracy for the four day period must be within ±5 msec relative to the shot time.

For crustal scale reflection experiments, instruments are deployed for three to five days with six to eight hour continuous recordings using a vibrator energy source. After each day’s recording, data is downloaded, and the Texan is initialized for the next day’s recording. Because the data may be stacked, time accuracy must be within ±2 msec.

Application

Active Source Crustal Studies
Refraction and Reflection Refraction and Reflection
Exploration 3-D Noise Testing Exploration 3-D Noise Testing
Tomographic Arrays Tomographic Arrays
Aftershock Studies Aftershock Studies
Micro-Zonation Survey Micro-Zonation Survey

Features

Low Power 24-Bit ADC: Low Power 24-Bit ADC:
Powered from 2 “D” Cell Batteries Powered from 2 “D” Cell Batteries
Small, Lightweight Small, Lightweight
Sealed Aluminum Case Sealed Aluminum Case
Solid-state Data Storage Solid-state Data Storage
Time Base Stability 0.1 ppm Time Base Stability 0.1 ppm
GPS Synchronization GPS Synchronization
Industry Standard Hi-Speed (480Mbit) Industry Standard Hi-Speed (480Mbit)
USB2.0 Interface USB2.0 Interface

System Operation

The self-contained Texan features a low-noise differential input amplifier, 24-bit analog-to-digital converter (ADC), solid-state data storage, and batteries, all in a sealed aluminum case. Up to 15 Texans are stored, setup, and transported. For setup, the Texans are connected to a hub that provides power, connection to the host computer via Hi-Speed USB2.0, and timekeeping signals from a GPS receiver.

The hub provides for 15 Texan connections, a connection to the USB host, and one port for daisy-chaining additional hubs. Several hubs can be operated in parallel allowing simultaneous connection between a single host computer and numerous Texans
Routes the 130-GPS Receiver/Clock signals to each Texan for synchronizing internal time to UTC and precisely setting the internal oscillator frequency
Supplies power to the Texans for setup and data retrieval

High Resolution Seismic Recorder

After setup, the Texans are deployed for recording. A state LED displays the operating condition of the Texan. This feature clearly informs the user that the battery voltage is sufficient, time is set, the acquisition program loaded, and the unit is either ready to acquire or is acquiring data. During the recording session, the Texan can be retimed or data may be downloaded to a laptop PC. At the conclusion of the experiment, the Texans are returned to the setup facility, retimed, and the data downloaded to the workstation for processing.