Open AccessObservations of Vertical and Lateral P ‐Velocityn Anomalies in the Earth'sMantle Using the Fennoscandian Continental Array
Author(s) -
Husebye E. S.,
Kanestrsm R.,
Rud R.
Publication year - 1971
Publication title -
geophysical journal of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.302
H-Index - 168
eISSN - 1365-246X
pISSN - 0016-8009
DOI - 10.1111/j.1365-246x.1971.tb02326.x
Subject(s) - classification of discontinuities , geology , geodesy , seismology , seismic velocity , range (aeronautics) , geophysics , mantle (geology) , travel time , seismic wave , mathematical analysis , materials science , mathematics , transport engineering , engineering , composite material
Summary The gross structure of the Earth'sinterior is fairly well known, but we are still lacking information on the finer details, i.e. structural discontinuities of higher orders. A powerful tool in investigations of this type of problem is P‐wave travel time, and specifically the parameter DT/DΔ . We have investigated this problem, taking advantage of the concept of continental arrays. Reported arrival time data (seismic bulletins) for the Fennoscandian network have been used for direct measurements of apparent velocity ( DT/DΔ ) and direction of approach of P ‐waves from 648 seismic events. Our observations are interpreted in terms of vertical anomalies at depths around 850, 1050, 1250, 1700 and 2600 km where the velocity changes very slowly with depth. The corresponding epicentral distances are 35, 47, 53, 62 and 87 deg. In addition, we have strong evidence for existence of lateral P ‐velocity variation which amounts to around 0‐1 km s –1 in the depth interval 1750–2300 km and the distance range is around 63–80 deg. A comparison of our data with those presented by others favours lateral velocity variations also at depths around 700–800 km and the corresponding distance range is 25–30 deg.