Geoscience Reference
In-Depth Information
Table 2.1 Common sources of environmental noise and the forms in which they manifest themselves for the various geophysical
methods. Specific details are included in the relevant chapters on each geophysical method.
Electrical and
electromagnetics
Source of noise
Gravity
Magnetics
Radiometrics
Seismic
Regolith
Changes in
thickness and
internal variations
in density causing
spurious
anomalies
Oxidation of magnetic
mineral species
Formation of
maghaemite causing
spurious anomalies
Concealment of bedrock
responses
Mobilisation of radioactive
materials causing
responses that are not
indicative of bedrock
High conductivity
leading to poor signal
penetration and
electromagnetic
coupling with
measurement array
Internal changes in
conductivity
(groundwater, clays)
causing spurious
anomalies
Superparamagnetic
behaviour (maghaemite)
Changes in
thickness and
internal changes
in velocity
affecting
responses
(statics)
Reduction in
the energy
transmitted from
source
Glacial
sediments
Changes in
thickness and
internal variations
in density causing
spurious
anomalies
Magnetic detritus
causing spurious
anomalies
Concealment of bedrock
responses
Mobilisation of radioactive
materials causing
responses that are not
indicative of bedrock
Internal changes in
conductivity causing
spurious anomalies
Changes in
thickness and
internal changes
in velocity
affecting
responses from
below (statics)
Permafrost and
snow cover
Changes in ice
content causing
spurious
anomalies
Concealment of bedrock
responses
Internal changes in
conductivity causing
spurious anomalies
Changes in
thickness and
internal changes
in velocity
affecting
responses from
below (statics)
Hydrological
Formation of low
density
dissolution
features in
carbonate rocks
causing spurious
anomalies
Dissolution/precipitation
(i.e. transportation) of
soluble radioactive
elements causing responses
that are not indicative of
the presence of K,
U and Th
Changes in groundwater
salinity causing changes
in conductivity
Movement of
electrolytes creating
spurious anomalies
Formation of
dissolution
features in
carbonate rocks
that scatter
seismic waves
Atmospheric
phenomena
Turbulence
during airborne
and ground
surveys
Turbulence during
airborne surveys
Turbulence during
airborne surveys
Uneven distribution of
radioactive aerosols
Movement of gaseous
radioactive species
Moisture suppressing
responses from the
ground
Turbulence during
airborne and some
ground surveys
Noise spikes due to
lightning strikes (sferics)
Wind (water
waves,
movement of
tree roots etc.)
and rain-related
noise
Extraterrestrial
phenomena
Temporal changes
in gravity due to
the position of the
Sun and Moon
Magnetic fields
associated with
processes occurring in
the ionosphere
Radioactivity of cosmic
origin
 
Search WWH ::




Custom Search