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There has been increasing field evidence for the presence of cross faults across the Himalaya. A number of these structures have been recognized at strike changes of the Main Frontal Thrust, but there is also evidence in the Greater Himalayan sequence for cross faults or transverse shear zones. Interestingly, there are also features from the seismic record that suggest that cross structures may concentrate some seismicity and that cross structures may limit the lateral propagation of thrust ruptures. A number of these structures align with structures on the Indian basement.
Cite as:
Hubbard, M.. (2020, July 19). Role of Cross Faults in Himalayan Tectonics.pdf (Version 1). Tectonics Community Science Workshop 2020. https://doi.org/10.6084/m9.figshare.12671024.v1
@article{Hubbard2020,
author = "Mary Hubbard",
title = "{Role of Cross Faults in Himalayan Tectonics}",
year = "2020",
month = "7",
url = "https://2020cigtectonics.figshare.com/articles/poster/Role_of_Cross_Faults_in_Himalayan_Tectonics_pdf/12671024",
doi = 10.6084/m9.figshare.12671024.v1}
Posted by Djordje on Jul 28th, 2020
Hi Mary.
Through the northern Sikkim, western Bhutan and its foreland we recognised a major strike slip seismic zone. It has also occasionally a strong topographic expression but i did not have a chance to make field observations. I think the slip along this structure is mostly in the Indian basement (lower plate) and is decoupled from the strike slip deformation in the Himalaya (the upper plate) by the Main Himalayan Thrust.
There is another, equivalent structure in the westernmost Bhutan and Assam. Following the comment by Sara Roeske, i think these seismic zones might be inherited transform faults (see the end of Discussion in my paper).
Here are our related papers.
Cheers,
Djordje
Diehl, T., Singer, J., Hetényi, G., Grujic, D., Clinton, J., Giardini, D., Kissling, E. and GANSSER Working Group. (2017) Seismotectonics of Bhutan: Evidence for segmentation of the Eastern Himalayas and link to foreland deformation. Earth and Planetary Science Letters, 471, 54-64. doi.org/10.1016/j.epsl.2017.04.038
Grujic, D., Hetényi, G., Cattin R., Baruah, S., Benoit, A., Drugkpa, D., and Saric, A. (2018) Stress transfer and connectivity between the Bhutan Himalaya and the Shillong Plateau. Tectonophysics. 744, 322–332, https://doi.org/10.1016/j.tecto.2018.07.018 .
also
Velasco, A. A., Gee, V. L., Rowe, C. Grujic, D., Hollister, L.S., Hernandez, D., Miller, K.C., Tobgay, T., Fort, M., and Harder, S. (2007): Using small, temporary seismic networks for investigating tectonic deformation: brittle deformation and evidence for strike-slip faulting in Bhutan. Seismological Research Letters, 78, 446-453.
Posted by Mary Hubbard on Jul 28th, 2020
Thanks Djordje. I will check out these papers. For the Nepal examples, the seismicity seems to be above and below the MHT, but perhaps it is driven by the basement faults. I feel like there is a lot we don't yet know about these structures. I appreciate your comments!