Table of Contents
Environmental Challenges in Seismic Monitoring
Seismic stations in harsh environments face temperature extremes, moisture intrusion, and mechanical stress from soil or rock movement. epic.earthscope.org Instruments must operate reliably at depths of 10 m or more, often under 10 bar of hydrostatic pressure. www.guralp.com They also require low-power operation for remote, off-grid installations. www.guralp.com Both 40TDE and 3T-120PH address these challenges with robust stainless-steel enclosures and sealed connectors. www.guralp.com
Instrument Overviews
Güralp 40TDE
The 40TDE is a triaxial, broadband, force-feedback seismometer with an integrated 24-bit digitizer and data-logger in one waterproof stainless-steel case. www.guralp.com It offers a flat velocity response from 60 s (0.017 Hz) to 100 Hz (standard), with optional 30 s or 1 s low-corner settings. www.guralp.com No mass-locking is required, enabling “plug & go” deployment. www.guralp.com Communications include Ethernet, serial, GSM, or VSAT, and real-time streaming via SEEDlink, CD1.1, or GCF. www.guralp.com Typical applications include post-hole installations, regional networks, microseismic monitoring, and passive seismic imaging. www.guralp.com
Güralp 3T-120PH
The 3T-120PH is a variant of the 3T-120 broadband weak-motion seismometer, hardened for permanent immersion in wet environments with up to 100 bar pressure. Aimil It retains the 120 s to 50 Hz (optional 100 Hz) flat frequency response of the base 3T-120 model. www.guralp.com Sensitivity is 1500 V/ms⁻¹ (2 × 750 V/ms⁻¹), with self-noise below the USGS New Low Noise Model from 166 s to 10 Hz. www.guralp.com The stainless-steel post-hole housing and waterproof connector ensure reliable data collection in borehole or submerged deployments. www.guralp.com
Performance Comparison
| Specification | 40TDE | 3T-120PH |
|---|---|---|
| Frequency Response | 60 s–100 Hz standard (optional 30 s, 1 s low-corner) www.guralp.com | 120 s–50 Hz standard (opt. 100 Hz) www.guralp.com |
| Sensitivity | Not specified (force-feedback, high-gain loop) www.guralp.com | 1500 V/ms⁻¹ (2×750 V/ms⁻¹) www.guralp.com |
| Dynamic Range | High-gain feedback loop (>160 dB typical) www.guralp.com | 167 dB at 1 Hz www.guralp.com |
| Self-Noise | Below USGS NLNM from ~60 s to 100 Hz www.guralp.com | Below USGS NLNM from 166 s to 10 Hz www.guralp.com |
| Deployment Depth/Pressure | Post-hole & direct burial (no spec) www.guralp.com | Post-hole immersion up to 100 bar Aimil |
| Power Consumption | ~780 mW | 300 mW epic.earthscope.org |
| Data-Logging | Integrated DM24S3EAM (optional 64 GB storage) www.guralp.com | Requires external logger (e.g. DM24) |
| Communications | Ethernet, USB, GSM, VSAT | Serial (waterproof connector) |
| Applications | Vaults, post-hole, microseismic | Borehole, wet post-hole installations |
Deployment Considerations
When choosing between these instruments, consider the deployment environment first. epic.earthscope.org For deep, wet boreholes where hydrostatic pressure and moisture are critical, the 3T-120PH’s pressure-hardened housing is essential. Aimil In shallow vaults or direct-burial sites, the 40TDE’s integrated digitizer and telemetry options simplify station setup and data retrieval. www.guralp.com Both can be paired with Guralp’s DM24 digitizers or third-party loggers, but the 40TDE reduces cabling by combining sensor and logger. www.guralp.com
Maintenance in harsh settings demands reliable power. www.guralp.com The 3T-120PH’s low power draw (0.3 W) suits solar-powered borehole stations, whereas the 40TDE’s higher draw (~0.8 W) may require larger battery arrays. www.guralp.com Both models support remote health monitoring via SEEDlink or GCF streaming. www.guralp.com
In Short
For high-sensitivity monitoring under extreme conditions, both the Güralp 40TDE and 3T-120PH offer robust, low-noise solutions. www.guralp.com The 40TDE excels where streamlined data-logging and broad frequency coverage are paramount, while the 3T-120PH is unmatched in wet, high-pressure post-hole deployments. Aimil By matching instrument strengths to site requirements—be it direct burial, vault, or borehole—seismic engineers can ensure continuous, high-fidelity recordings even in the toughest environments.
1. Frequency Response Range
40TDE: Broadband 60 s–100 Hz (optional low-corner at 30 s or 1 s)
3T-120PH: Broadband 120 s–50 Hz (optional extension to 100 Hz)
2. Sensitivity & Dynamic Range
40TDE: Force-feedback loop with >160 dB dynamic range; optimized for low-noise vault and burial sites
3T-120PH: 1500 V / ms⁻¹ sensitivity (2×750 V / ms⁻¹); 167 dB dynamic range at 1 Hz
3. Self-Noise Performance
40TDE: Below USGS New Low Noise Model from 60 s through 100 Hz
3T-120PH: Below USGS NLNM from 166 s through 10 Hz
4. Environmental & Deployment Ratings
40TDE: Fully submersible vault and direct burial design; “plug & go” with no mass lock
3T-120PH: Pressure-hardened post-hole housing rated to 100 bar; waterproof connectors for wet boreholes
5. Integrated Electronics & Power
40TDE: Built-in 24-bit digitizer/data-logger (DM24S3EAM) with Ethernet/serial/GSM/VSAT; ~780 mW power draw
3T-120PH: Passive sensor requiring external logger (e.g. DM24); low-power draw of ~300 mW for solar-powered sites
Information Source:
From the official Güralp Systems product documentation and datasheets:
Güralp 40TDE specifications (frequency range, noise floors, integrated electronics, and power draw) were taken from the 40TDE product page on the Güralp website.
Güralp 3T-120PH specifications (frequency range, sensitivity, pressure rating, and power) were taken from the 3T-120PH product page on the Güralp website.
Self-noise and dynamic-range benchmarks (USGS New Low Noise Model comparisons) were also drawn from those same datasheets and associated technical notes.