TY - JOUR

T1 - Correction for geomagnetic secular variation effects: A new method (case study of the altai geodynamic network)

AU - Kuleshov, D. A.

AU - Dyadkov, P. G.

AU - Plotkin, V. V.

N1 - Funding Information: The study was carried out as part of Government Assignment 033120190012 and was partly supported by grant 17-05-01234-a from the Russian Foundation for Basic Research. Publisher Copyright: © 2021, V.S. Sobolev IGM, Siberian Branch of the RAS.

PY - 2021/2

Y1 - 2021/2

N2 - The study focuses on detection of geomagnetic secular variation and the respective correction of tectonomagnetic data. A new technique is proposed for picking the secular variation component in the Earth’s main magnetic field recorded by precise measurements at 100 to 500 km sites on the surface. Long-period field variations presumably arise from fluid motions in the liquid core, at depths of 3000 km, whereas the sizes of observation networks are within 500 km. The sources of secular variation, irrespective of their configuration, are much deeper than those of tectonomagnetic anomalies located above the Curie surface depths of ~10 to 20 km. Therefore, the surfaces that represent the space distribution of secular variation must be smoother than the respective surfaces for tectonomagnetic anomalies. The problem is thus to separate the regional and local signals from the two types of sources located at different depths. The new method is tested using data of yearly geomagnetic measurements at more than 30 repeat stations of a ~120 km long geodynamic network in Gorny Altai spanning the period from 2004 through 2018. The secular variation pattern is reconstructed by quadratic interpolation. The precise data cor-rected for secular variation of the main field reveal previously hidden tectonomagnetic anomalies up to 12 nT. The 3 nT positive anomaly falls within the zone of surface deformation caused by the Mw = 7.3 Chuya earthquake of 27 September 2003.

AB - The study focuses on detection of geomagnetic secular variation and the respective correction of tectonomagnetic data. A new technique is proposed for picking the secular variation component in the Earth’s main magnetic field recorded by precise measurements at 100 to 500 km sites on the surface. Long-period field variations presumably arise from fluid motions in the liquid core, at depths of 3000 km, whereas the sizes of observation networks are within 500 km. The sources of secular variation, irrespective of their configuration, are much deeper than those of tectonomagnetic anomalies located above the Curie surface depths of ~10 to 20 km. Therefore, the surfaces that represent the space distribution of secular variation must be smoother than the respective surfaces for tectonomagnetic anomalies. The problem is thus to separate the regional and local signals from the two types of sources located at different depths. The new method is tested using data of yearly geomagnetic measurements at more than 30 repeat stations of a ~120 km long geodynamic network in Gorny Altai spanning the period from 2004 through 2018. The secular variation pattern is reconstructed by quadratic interpolation. The precise data cor-rected for secular variation of the main field reveal previously hidden tectonomagnetic anomalies up to 12 nT. The 3 nT positive anomaly falls within the zone of surface deformation caused by the Mw = 7.3 Chuya earthquake of 27 September 2003.

KW - Altai geodynamic network

KW - Geomagnetic field

KW - Interpolation fit

KW - Secular variation

KW - Tectonomagnetism

UR - http://www.scopus.com/inward/record.url?scp=85106262350&partnerID=8YFLogxK

UR - https://www.elibrary.ru/item.asp?id=46074504

UR - https://www.mendeley.com/catalogue/0b8872bd-0bd6-3ad3-8590-6810f23e1863/

U2 - 10.2113/RGG20194056

DO - 10.2113/RGG20194056

M3 - Article

AN - SCOPUS:85106262350

VL - 62

SP - 255

EP - 262

JO - Russian Geology and Geophysics

JF - Russian Geology and Geophysics

SN - 1068-7971

IS - 2

M1 - 8

ER -