Integrated seismic investigations across the Mersey Estuary, Halton District, UK

Abstract

Acombined terrestrial and marine seismic investigation has been undertaken of the Inner Mersey Estuary, Halton District, UK, prior to construction of a major new river crossing. Much of the site lies on inter-tidal sand and mud bars accessible only for restricted periods and is unsuited to prolonged physical investigations using heavy plant. The investigation included high-resolution seismic refraction and reflection surveying on the salt marsh and inter-tidal regions, plus sub-bottom profiler investigation of the main river channel. Strategically located boreholes followed the geophysical work. Results show that the current configuration of the Inner Mersey Estuary is largely unrelated to the underlying bedrock geometry. In the area surveyed, the River Mersey is located on the southern flank of a buried elongate depression in the bedrock surface whose approximate position has been investigated previously between Ditton Marsh and Warrington through the interpretation of borehole records. The results also demonstrate a clear increase in compressional ( P ) wave seismic velocity of the Triassic sandstone with age, allowing the possible detection of an important fault. This paper highlights the potential for saving project capital through a properly designed geophysical site investigation prior to the commencement of major civil engineering projects.

Mixed method approaches to the investigation and mapping of buried Quaternary deposits: examples from southern England

“…Similar arguments have been made by those involved in geotechnical studies associated with engineering construction activities (Culshaw, 2005;Lenham et al, 2005). Characterization of the ground conditions in order to determine appropriate construction methods generally occurs in the initial stages of project development and may involve a range of techniques including borehole, CPT and geophysical techniques.…”

The geophysics contributions from the QJEGH , 1967 – 2015

“…on techniques to investigate shallow geological structures down to depths of 100 m, which included three basic principles papers by Hill (1992a) on field sources, geophone arrays and recording instruments, King (1992) on the common mid-point survey configuration and resulting field records and the excellent paper by on reflection seismic processing. Much good practice used 24 channel systems and high frequency, explosive sources to produce reflection seismograms for lithostratigraphic interpretation, such as, the Mercia Mudstone overlapping Charnian by Hill (1992b) aiding gypsum mining in Leicestershire, and the mapping of foundation conditions by Nichol & Reynolds (2002) who mapped glaciolacustrine infill over Silurian Flagstones for the A5 bridge replacement at Pont Melin Rug, and Lenham et al (2005) who mapped the Runcorn Sands (and silts) over Triassic sandstone in the Mersey Esturary. Meeks (1992) obtained long duration seismograms but with high frequency/resolution in the fully saturated fluviatile and coastal sands of Rucphen, Netherlands.…”

3D reconstruction of a shallow archaeological site from high-resolution acoustic imagery: The Grace Dieu

“…It should be noted that if the reflection coefficient was positive, then the same modulus values would give a conventional density that ranges between 727 kg/ 3 and 857 kg/m 3 . This is a totally unrealistic value since fresh, undegraded oak has a conventional density of 580 kg/m 3 . This further supports the idea that the reflection coefficient, related to the timbers of the Grace Dieu, should have a negative polarity.…”

“…[1][2][3][4][5]). However, high-resolution marine acoustic surveying for buried objects in the shallow waters of the inter-tidal to immediate sub-tidal zone is still a major challenge.…”