First Draft of the README file completed.

README.md

@@ -1,3 +1,145 @@
 # Mitchell_2022_CLVF_Gravity
 
-This repository contains all of the files required to reproduce the SimPEG gravity inversions run using the dataset from the CLVF.
+This repository contains all of the files required to reproduce the SimPEG gravity inversions of the CLVF field dataset.
+
+
+Gravity dataset
+-----------------------------------------------------------------------------------------------------------
+File names: groundGrav_Combined_zEllipsoid_Full.pkl
+            groundGrav_Combined_zEllipsoid_Full.csv
+
+For this study, a regional CLVF gravity dataset was compiled that includes 2,929 gravity stations. Measurements
+used in this study include the dataset collected by Langenheim et al. (2006), datasets from
+Chapman and Bishop (1974), Youngs et al. (1985), and Smith (1992) compiled by Langenheim et al. (2006), and a
+2018 dataset collected in The Geysers (Peacock et al., 2020). All of the raw measurements were processed using
+the standard gravity reduction methods outlined in Blakely (1995) to produce the complete Bouguer anomaly (CBA)
+and isostatic residual gravity anomaly. The CBA includes the terrain correction, computed using BOUGUER
+(Godson and Plouff, 1988), which accounts for the gravitational attraction of terrain above sea level. The
+residual isostatic gravity anomaly, which accounts for regional variations in the upper mantle and lower crust
+that compensate topographic loads, were calculated in the manner of Simpson et al. (1986). Additional details
+regarding the standard USGS gravity reduction techniques used here can be found in Langenheim et al. (2006) and
+Langenheim et al. (2007).
+
+The field dataset is provided in two different formats (.csv and .pkl). Both datafiles were created from a Pandas
+Dataframe with 12 data columns: Station_ID, lonWGS84, latWGS84, xWGS84_UTM10N, yWGS84_UTM10N, zWGS84, OG, FAA,
+SBA, TTC, CBA, and ISO.
+
+Station_ID: Name/ID assigned to the gravity station
+lonWGS84: Longitude of the gravity station (CRS: WGS84)
+latWGS84: Latitude of the gravity station (CRS: WGS84)
+xWGS84_UTM10N: Easting of the gravity station [m] (CRS: WGS84, Zone 10N)
+yWGS84_UTM10N: Northing of the gravity station [m] (CRS: WGS84, Zone 10N)
+zWGS84: Height of the gravity station above the WGS84 ellipsoid [m]
+OG: Original (raw) gravity meansurement [mGal]
+FAA: Free-Air anomaly [mGal]
+SBA: Simple Bouguer Anomaly [mGal]
+TTC: Total Terrian Correction [mGal]
+CBA: Complete Bouguer Anomaly [mGal]
+ISO: Residual isostatic gravity anomaly [mGal]
+
+Gravity corrections were calculated using station locations based on the NAD27 CRS and the NVD29 vertical
+datum. Absoluted gravity measurements were calculated using the 1967 formula based on the IGSN71 datum. For
+consistency with the SRTM DEM gravity station locations were transformed into lat,lon and UTM coordinates
+based on the WGS84 CRS and the WGS84 ellipsoid.
+
+
+
+Mesh File
+-----------------------------------------------------------------------------------------------------------
+File name: GroundGravCombined_InvMesh_BaseCell_200_200_50_50kmPad.msh
+
+OcTree mesh file saved in UBC-GIF format.
+
+4096 4096 16384                         # Number of base cells in x, y, and z directions
+107357.3290 3887596.6230 410325.0000    # Top SW corner of the mesh [m]
+200.000 200.000 50.000                  # Base cell (smallest cell) size in x, y, and z directions [m]
+3575380                                 # Total number of cells in mesh
+1 1 1 2048                              # i,j,k (indices of cell location) and cell size relative to base cell
+2049 1 1 2048
+1 2049 1 2048
+2049 2049 1 2048
+
+
+
+Active Cells File
+-----------------------------------------------------------------------------------------------------------
+File name: actCellTopoInd_200_200_50.npy
+
+(# Cells,) Numpy boolean array which is True if the cell is active (below the topographic surface) and False
+if the cell is inactive (air cell above topography).
+
+
+
+Cell Weights File
+-----------------------------------------------------------------------------------------------------------
+File name: cellWeights_Depth.npy
+
+(# Active Cells,) Numpy array containing a cell weights for each active cell in the octree mesh. These cell
+weights are based off a depth weighting which counteracts the natural ( 1/z^2) decay of the gravity kernel
+function (Li and Oldenburg, 1998).
+
+
+
+Inversion Script
+-----------------------------------------------------------------------------------------------------------
+File name: Inv_PGI_grav_5units_depthWieght_TikhonovReg_dObsNeg.py
+
+Python script to setup and run the field dataset 5 unit Petrophysically and Geologically Guided Inversion
+(PGI) See Astic and Oldenburg, (2019) for details.
+
+
+
+Recovered Model File
+-----------------------------------------------------------------------------------------------------------
+File name: rhoInv_groundGravCombined_generalBounds_PGI5_depthWeight_dObsNeg.npy
+
+(# Cells,) Numpy array containing the recovered density contrast model from the 5 unit PGI.
+
+
+Predictive Data File
+-----------------------------------------------------------------------------------------------------------
+File name: dPred_mInv_groundGravCombined_generalBounds_PGI5_depthWeight_dObsNeg.npy
+
+(# Data,) Numpy array containing the predicted data from the recovered density contrast model. Data residuals
+can be calculated by subtracting these prediceted data from the observed data.
+
+
+References:
+-----------------------------------------------------------------------------------------------------------
+Astic, T., Oldenburg, D.W., 2019. A framework for petrophysically and geologically guided
+geophysical inversion using a dynamic Gaussian mixture model prior. Geophysical Journal
+International 219, 1989–2012. doi:10.1093/gji/ggz389.
+
+Blakely, R.J., 1995. Potential Theory in Gravity and Magnetic Applications. Cambridge
+University Press, Cambridge. doi:10.1017/CBO9780511549816.
+
+Chapman, R.H., Bishop, C.C., 1974. Bouguer gravity map of California, Santa Rosa sheet.
+Technical Report.
+
+Langenheim, V.E., Jachens, R.C., Morin, R.L., McCabe, C.A., 2007. Preliminary Gravity
+and Magnetic Data of the Lake Pillsbury Region, Northern Coast Ranges, California.
+Technical Report. U.S. Geological Survey.
+
+Godson, R.H., Plouff, D., 1988. BOUGUER Version 1.0 : a microcomputer gravity-terrain-
+correction program. Technical Report. U.S. Geological Survey. doi:10.3133/ofr88644B.
+
+Langenheim, V.E., Roberts, C.W., McCabe, C.A., McPhee, D.K., Tilden, J.E., Jachens,
+R.C., 2006. Preliminary Isostatic Gravity Map of the Sonoma Volcanic Field and Vicinity,
+Sonoma and Napa Counties, California. Technical Report. U.S. Geological Survey. doi:10.
+3133/ofr20061056.
+
+Li, Y., Oldenburg, D.W., 1998. 3-D inversion of gravity data. Geophysics 63, 109–119.
+doi:10.1190/1.1444302.
+
+Peacock, J.R., Earney, T.E., Mangan, M.T., Schermerhorn, W.D., Glen, J.M., Walters, M.,
+Hartline, C., 2020. Geophysical characterization of the Northwest Geysers geothermal
+field, California. Journal of Volcanology and Geothermal Research 399, 106882. doi:10.
+1016/j.jvolgeores.2020.106882.
+
+Smith, N., 1992. Gravity interpretation of San Pablo Bay and vicinity, in: Wright, T.L. (Ed.),
+Field trip guide to Late Cenozoic geology in the North Bay region. Northern California
+Geologic Society, pp. 71–80.
+
+Youngs, L.R., Chapman, R.H., Chase, G.W., 1985. Complete Bouguer gravity and aeromag-
+netic maps with geology and thermal wells and springs of the Santa Rosa-Sonoma area, Sonoma
+and Napa counties, California. Technical Report. California Division of Mines and Geology.