Marine Geophysical Surveys

MHS provides a comprehensive marine geophysical service. The primary marine geophysical services offered by MHS are Sub-Bottom Profiling and 2D Marine Seismic Reflection Surveys. This type of profiling and surveys are performed to provide accurate detail of sub seabed strata for port development investigations, oil rig site surveys, foundation investigations, offshore construction, pipeline and cable route surveys and dredging investigations.

 

2D Marine Reflection Geophysical

MHS has developed a high-resolution multi-channel surface towed 2D Marine Reflection Seismic (MaRS) System to address the growing need for port development and marine infrastructure engineering investigations to acquire higher resolution geophysical data to a greater depth of penetration and through harder materials than commonly associated with traditional sub-bottom profiling systems. MaRS MKII also solves the challenges that arise when using traditional systems to acquire geophysical data in nearshore and very shallow water operations. MaRS MKIII negates the environmental constraints associated with using even a single low powered Air Gun as the Seismic Source.

Based on the well proven 2D seismic technology from the offshore oil industry and using specialised sound sources and highly sensitive hydrophone streamers with matched frequency response from 10Hz to 2.5kHz, MaRS MKII and MKIII produce High-Resolution Reflection Seismic Profiles of sub seabed strata and determine Compressional P-wave velocities to a depth of penetration greater than 50 metres in seabed materials from soft sediments with P-wave velocities of 1540m/s to weathered and fractured materials with P-wave velocities above 2800m/s. Correlation of P-wave velocities with ‘Reflection Profile’ stratification data provides valuable information for maritime engineering projects.

 

Seismic Line N 780 Processed

Seismic-Line-N-780-Processed

 

 

Seismic Line N 780 Reduced to Datum  
Seabed to Reflector 1 Silty Clay 1580 m/s to 1780 m/s
Reflector 1 to Reflector 2 Sandy Silty Clay 1620 m/s to 1800 m/s
Reflector 2 to Reflector 3A Stiff Clayey Sands 1670 m/s to 1980 m/s
Reflector 3A to Reflector 3 Compacted Sediments 1700 m/s to 2000 m/s
Reflector R3 to Reflector R4 Cemented Sediments  1800 m/s to 2000 m/s

 

MHS high-resolution 2D Marine Reflection Seismic System produces conventional profiles of Reflection Seismic “Reflectors” and also measures reliable Compressional “P-wave velocities” within these reflectors. Correlation of Compressional P-wave velocities through materials in situ strength provides very useful information for engineering projects such as dredging and piling.

 

Mapping and Hydrographic Surveys Pty Ltd now offers this new High Resolution 2D Marine Reflection Geophysical capability to the Ports and Maritime Engineering Community.

 

Sub-Bottom Profiling

For shallow penetration work, MHS operates a range of high-resolution sub-bottom profilers including 3.5kHz and 10kHz PINGERS, 3.5kHz CHIRP and 500Hz BOOMERS. For surveys involving the mapping of only a few metres beneath a soft mud seabed, PINGER and CHIRP systems are often useful due to the high resolution of the sub seabed strata. For penetration in stiffer materials, BOOMER systems are used however these systems are a single channel and are limited in their application.