TY - JOUR
T1 - A new methodology to estimate magnetotelluric (MT) tensor relationships
T2 - Estimation of Local transfer-functions by Combining Interstation Transfer-functions (ELICIT)
AU - Campanyà, Joan
AU - Ledo, Juanjo
AU - Queralt, Pilar
AU - Marcuello, Alex
AU - Jones, Alan G.
PY - 2014/7
Y1 - 2014/7
N2 - A new methodology to estimate magnetotelluric (MT) tensor relationships, called Estimation of Local transfer-functIons by Combining Interstation Transfer-functions (ELICIT), is proposed whereby the MT tensor relationships of the local site are derived using only interstation transfer functions. The MT impedance tensor and the geomagnetic transfer function at the local site are characterised by combining interstation tensor relationships between electric and magnetic fields at the local site with the horizontal magnetic fields acquired at a neighbouring site. The main property of the proposed method is that the employed interstation transfer functions are independently constrained, without the need to acquire the electric and the magnetic fields at the local site simultaneously to recover the local MT tensor relationships. Due to this property, the ELICIT method offers new possibilities for MT data acquisition and processing, providing significant improvements when the magnetic time-series at the local site are affected by local noise or are truncated. Error analysis shows that, even when magnetic fields are truncated, the quality of the results obtained following the ELICIT method are similar to those we would obtain if the magnetic fields had not been truncated. Another important property is that different neighbouring sites can be used to recover the tensor relationships at the local site. Averaging of results obtained using different neighbouring sites can be performed to improve the statistics. For our example data, when the ELICIT method is used to improve the statistics, errors of the estimates for periods between 1000 and 20 000 s periodicities are clearly reduced. All interstation transfer functions are calculated doing remote reference and the bootstrap method is used to compute the errors, when necessary. Long period magnetotelluric data acquired in the Pyrenees and in the Atlas Mountains in Morocco, and magnetic data provided by Fürstenfeldbruck magnetic observatory have been used to test the proposed ELICIT method, with positive results. Due to the lack of requirement that the electric and the magnetic fields of the local site be acquired simultaneously, the proposed method also offers new possibilities for MT data acquisition, optimizing the available instrumentation.
AB - A new methodology to estimate magnetotelluric (MT) tensor relationships, called Estimation of Local transfer-functIons by Combining Interstation Transfer-functions (ELICIT), is proposed whereby the MT tensor relationships of the local site are derived using only interstation transfer functions. The MT impedance tensor and the geomagnetic transfer function at the local site are characterised by combining interstation tensor relationships between electric and magnetic fields at the local site with the horizontal magnetic fields acquired at a neighbouring site. The main property of the proposed method is that the employed interstation transfer functions are independently constrained, without the need to acquire the electric and the magnetic fields at the local site simultaneously to recover the local MT tensor relationships. Due to this property, the ELICIT method offers new possibilities for MT data acquisition and processing, providing significant improvements when the magnetic time-series at the local site are affected by local noise or are truncated. Error analysis shows that, even when magnetic fields are truncated, the quality of the results obtained following the ELICIT method are similar to those we would obtain if the magnetic fields had not been truncated. Another important property is that different neighbouring sites can be used to recover the tensor relationships at the local site. Averaging of results obtained using different neighbouring sites can be performed to improve the statistics. For our example data, when the ELICIT method is used to improve the statistics, errors of the estimates for periods between 1000 and 20 000 s periodicities are clearly reduced. All interstation transfer functions are calculated doing remote reference and the bootstrap method is used to compute the errors, when necessary. Long period magnetotelluric data acquired in the Pyrenees and in the Atlas Mountains in Morocco, and magnetic data provided by Fürstenfeldbruck magnetic observatory have been used to test the proposed ELICIT method, with positive results. Due to the lack of requirement that the electric and the magnetic fields of the local site be acquired simultaneously, the proposed method also offers new possibilities for MT data acquisition, optimizing the available instrumentation.
KW - Electromagnetic theory
KW - Magnetic and electrical properties
KW - Magnetotellurics
UR - http://www.scopus.com/inward/record.url?scp=84905920027&partnerID=8YFLogxK
U2 - 10.1093/gji/ggu147
DO - 10.1093/gji/ggu147
M3 - Article
AN - SCOPUS:84905920027
SN - 0956-540X
VL - 198
SP - 484
EP - 494
JO - Geophysical Journal International
JF - Geophysical Journal International
IS - 1
ER -