Bedrock depth is one of the critical site investigation procedures for seismic hazard analysis and
underground developments that may encounter varying rock formation. The rock that underlies looser
surface material. Bedrock is the solid, intact part of the earth’s crust, the outer layer 20-25 miles
thick that rests on the earth’s mantle. In most places in Maine, the bedrock is concealed by a thin
veneer of unconsolidated sediment, soil, and vegetation. An exposed portion of bedrock is often
called an outcrop. The various kinds of broken and weathered rock material, such
as soil and subsoil that may overlie the bedrock are known of the bedrock beneath the soil cover
regolith is also known engineering geology and its identification by digging. Weathering may be
physical or chemical and alters the structure of the rock and may cause it to erode and or alter over
time based on the interactions between the mineralogy and its interactions.
Noise seismic data from Cape Cod produced clear, easily identified resonance frequency peaks. The interpreted depth and geometry of the bedrock surface correlate well with boring data and previously published seismic
refraction surveys. Conversely, the ambient noise seismic data from eastern Nebraska produced
subtle resonance frequency peaks, and correlation of the interpreted bed rock surface with
depths from borings is poor, which may indicate a low acoustic impedance contrast between the
weathered sedimentary rock and overlying sediments and the effect of wind noise on the seismic
records. Local estimates of bedrock depth likely could be improved through development of
regional or study‐area‐specific regression equations relating resonance frequency to
depth.
To assess the subsurface strata and to locate the particular depth of rock, most of the site
investigation practices typically follow conventional programs which involve traditional drilling,
sampling, and laboratory testing as well as specific in-situ test. The new empirical correlation is
established between the natural frequency of the ground calculated from the MM and the bed rock
depth from conventional borehole drilling towards. Understanding the global pattern of
underground boundaries such as groundwater and bed rock occurrence is of continuous interest to
Earth and geosciences.
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