. Collected reprints / Atlantic Oceanographic and Meteorological Laboratories [and] Pacific Oceanographic Laboratories. Oceanography 234 McGregor et al.: Magnetics Mid-Atlantic Ridge. Fig. ^. Profiles of bathymetry, magnetization, and magnetic anomaly (see Figure 2 for location). Magnetic reversal chronology is from Talwani et al. [l97l]. Axis line represents present-day location of spreading. Hatched area under bathymetry indicates region of faulted blocks which can be traced from profile to profile. Arrows indicate low in axial anomaly. Initially used to smooth the data prior t
. Collected reprints / Atlantic Oceanographic and Meteorological Laboratories [and] Pacific Oceanographic Laboratories. Oceanography 234 McGregor et al.: Magnetics Mid-Atlantic Ridge. Fig. ^. Profiles of bathymetry, magnetization, and magnetic anomaly (see Figure 2 for location). Magnetic reversal chronology is from Talwani et al. [l97l]. Axis line represents present-day location of spreading. Hatched area under bathymetry indicates region of faulted blocks which can be traced from profile to profile. Arrows indicate low in axial anomaly. Initially used to smooth the data prior to pro- filing was left in the analysis sequence prior to filtering, amounting to some modulation of the band-pass filter described above. This combined smoothing technique did not appreciably change the appearance of the magnetic anomaly. The depth-to-block D versus the width-of-block w ratio has been shown by Bott and Button [1970] and Blakely and Schouten [197AJ to be important in the separation of noise from data, when the short-period behavior of the earth's magnetic field is studied. Their criterion of D/2w i 1 is essentially met in our treatment in that the short-wavelength cutoff of the filter Xgnil> which is twice the effective sampling interval Wgff, is such that D/Agn,i = D/2weff = 1. The magnetic anomaly pattern on this portion of the Mid- Atlantic Ridge (Figure 4) does not show the short-period events in the magnetic reversal chronology. Therefore we wish to focus atten- tion on the general trends of the magnetization pattern. In Figure 4 the line down the center of each profile represents the present axis of spreading in the rift valley. The axis was positioned by the medial ridge where it was present and other- wise by the deepest part of the rift valley. The positive zone of magnetization, approximately 25 km wide in the center of each profile, and the associated positive anomaly represent the axial anomaly. On either side of this zone is a section of negative
Size: 1394px × 1793px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., book, bookcentury1900, bookcollectionamericana, bookleafnumber249
