Jacobsen Filter
– a Spectral
Domain filter that enhances the residual components of the
gravity or magnetic fields by calculating the difference between two Wiener
Filter-based upward continuations or applying the modified Upward
Continuation in accordance with a specified “pass-above” or
“pass below” depth. J.F.
is also referred to as Separation Filter. [48,
118].
Julian Date
– a date of
the magnetic or gravity survey observations, recorded by the digital acquisition
system as a four-digit value, which represents Julian
Day and the year of
the survey. For example, the value of 3399 (or 9933) corresponds to February 2,
1999.
Julian Day
– the
day’s ordinal number since January 1 of the current year. J.D. is used as standard input parameter for digital records of
the magnetic or gravity acquistion data. See Julian Date.
Julians
– a list of
Julian days in the dataset of the gravity or magnetic observations. See Julian
Day.
Juvenile
– a term
applied to water, gas or ore-forming fluids originating from Magma
as opposed to fluids of the surface origin. J. fluids may significantly contribute to the magnetization of
intra-sedimentary and intra-basement faults or fracture zones. J. water is also referred to as Plutonic
Water. [13].
See Magnetized Intra-basement Fault and Magnetized Intra-sedimentary Fault.
Juxtaposition
– side-by-side position of specified tectonic blocks,
magnetic terranes and other subsurface structural elements identified on the
basis of the potential field data interpretation. See Magnetic
Terrane and Tectonic
Province.