Terraloc Pro Seismograph


A seismograph is a versatile instrument and can be used in several applications and for many kind of measurements. Although some functionality is application specific, a seismograph is very much a generic data-logger with emphasis on analyzing time and frequency. The Terraloc Pro takes the concept of versatility even further as it offers superior performance in amplitude accuracy and linearity. Thus the Terraloc Pro is design to target applications beyond the traditional seismic survey i.e. such as vibration analysis and other monitoring applications. ABEM will carefully watch the market and strategically support selected applications with added functionality.

Refraction seismology:

The most common method used in the fields of engineering geology, geotechnical engineering and exploration geophysics. The methods depend on the fact that seismic waves have differing velocities in different types of soil (or rock). The waves are refracted when they cross the boundary between different types (or conditions) of soil or rock. The methods enable the general soil types and the approximate depth to strata boundaries, or to bedrock, to be determined.

Reflection seismology:

By the time it takes for a reflection to arrive at a receiver, it is possible to estimate the depth of the feature that generated the reflection. In this way, reflection seismology is similar to a sonar (echosounding).  Reflection seismology is extensively used in exploration for hydrocarbons (i.e., petroleum, natural gas) and such other resources as coal, ores, minerals, and geothermal energy. Reflection Seismology is also used in shallow application for engineering, groundwater and environmental surveying.

Borehole tomography:

Cross-hole seismic surveysinvolve measurement of the travel time of seismic energy transmitted between two or more boreholes in order to derive information on the elastic properties of the intervening materials. One hole is used to deploy the source whilst the other hole(s) are used to detect the arrival of the seismic energy. The travel times of the seismic waves are derived from the first-arrivals identified on the seismic trace for each shot-receiver position and are used with the known distance(s) between the shot/receiver boreholes to calculate the apparent velocities (P and S) for each depth interval. This data is then used to derive a vertical profile of the various elastic module.

Borehole seismic tomography involves the measurement of the travel times of seismic raypaths between two or more boreholes in order to derive an image of seismic velocity in the intervening ground. Data is collected using one hole for the seismic source (normally a sparker) and measuring first-arrival times using strings of hydrophones in the others. Travel times are collected at regular intervals (usually 0.5m to 2m) all the way down the hole(s) for each shot position. This results in a network of overlapping raypaths that can then be used to model the velocity profile. The resulting velocity image is termed a tomogram and enables identification of anomalous velocity zones lying between the boreholes as well as imaging individual velocity layers.


Vertical seismic profiling is the simplest and cheapest borehole seismic techniques and requires only a single borehole. Seismic energy is generated on surface at a fixed distance from the top of the borehole. The travel times of the first-arrival seismic waves are measured at regular intervals down the hole using a string of hydrophones or, in the case of S-wave surveys, a single clamped triaxial geophone that is gradually moved down the hole. The P- and S-wave arrival times for each receiver location are combined to produce travel-time versus depth curves for the complete hole. These are then used to produce total velocity profiles from which interval velocities and the various elastic moduli can be calculated.


Multichannel analysis of surface waves (MASW) method is one of the seismic survey methods evaluating the elastic condition (stiffness) of the ground for geotechnical engineering purposes. MASW first measures seismic surface waves generated from various types of seismic sources, analyses the propagation
velocities of those surface waves, and then finally deduces shear-wave velocity (Vs) variations below the surveyed area that is most
responsible for the analyzed propagation velocity pattern of surface waves. Shear-wave velocity (Vs) is one of the elastic constants. Under most circumstances, Vs is a direct indicator of the ground strength (stiffness) and therefore commonly used to derive load-bearing capacity. After a relatively simple procedure, final Vs information is provided in 1-D, 2-D, and 3-D formats.  


Most commonly a reflection seismic surveys conducted from a vessel. The energy source in use can be air guns, water guns and vibrators. The period between shots would typically be a few seconds. Then signal is picket up be arrays of hydrophones (instead of geophones) often called streamers. In addition the seismic signals, a timestamp synchronized to the shot, speed of the vessel and depths may be collected and fed to the seismograph.

Earthquake monitoring:

Terraloc Pro is design to measure in the low frequency region (tens of Hertz) required for Earthquake monitoring. For automatic picking (triggering) of such signal a picking algorithm is required. Commonly a STA/LTA (Short Time Average over Long Time Average) type algorithm is used to trigger on incoming data stream. This feature is not currently available but may be implemented (in software) on a demand from the market.

Blast and vibration measurements.

Vibrations caused by blasting must be controlled not to exceed set and defined limits (by regulations or by an issued risk-analysis). With a proper process in place, production (fragmentation) can be maximized and the risk of damage to surrounding structures can be minimized. The Terraloc Pro can handle the full dynamic range of a geophone (0-250 mm/s) used to measure vibrations i.e. as a result blasting, piling or other construction work. For monitoring purposes it must be possible to trig on any (or a combination of) input channel with individually configurable trigger (threshold) levels.

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