1. How might borehole gravity observations from 3 or more boreholes be used to l
ID: 297673 • Letter: 1
Question
1. How might borehole gravity observations from 3 or more boreholes be used to locate a subsurface body of anomalous density that has not been intersected by any of the boreholes?
2. Errors which are inherent in geophysical data propagate as various mathematical processes are performed. For a set of 17 observations with the mean value 2.06 and standard deviation 0.32 and another set of 39 observations with a mean of 4.54 and standard deviation of 0.26, calculate the
(a) sum,
(b) difference,
(c) product, and
(d) quotient of these data, including (e) their combined standard deviation.
3. The potential of g is G = (x2 + y2)1.
(a) Find g.
(b) Describe the field lines, and
(c) equipotential surfaces of g.
(d) Demonstrate by integrating around the perimeter of a rectangle in the (x, y)-plane that g is conservative.
Explanation / Answer
1. When gravity measurements are recorded in 3 or more boreholes bracketing a massive body.
A sequence of precise gravity measurements are gathered at discreet intervals by pause and reading the gravimeter at predefined borehole depths. After that corrections applied to these gravity measurements. The correction are such as free air anomaly, bouguer anamoly, gravity drift , latitutde, surface topgraphy etc. Applying these corrections, the residual gravity data provides information about the distribution of rock densitites in both in the vicinity of the hole and away from it.
Inversion routine and forward modeling and inversion routines (co-rigging) can be used to construct a 3 dimensional representation of the subsurface body from these distribution. Subsurface body of anomalous density can be detected by such 3 D profiles.
2. Sum=A+B=6.600, A-B= -2.480, A*B=9.352, A/B=0.458 and new std dev=sqrt(0.36^+0.26^2)=0.44
3. if G is a conservative vector field then g is potential
(a) g can calculated by integrating G thus we have g =x3/3+y3/3+x+y as del(g)=F in a conservative field
(b)potential joining in x -y plane gives field line
(c).The line having the same potentiall is the equipotential line and and surface having same potential is equipotential surface.
(d) consider the four coordinate of the rectangle as x1,y and x2,y and x2, y2 and x1,y2 in anticlockwise direction of a rectangle and integration of F.dr gives workdone and will be zero in conservative field.
Do four integration for four lines and later sum all. its result will be 0
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.