Bulletin of the Geological Society of Malaysia, Volume 70, November 2020, pp. 125 – 132

Active tectonics and active faults: Why these terms still lack consensus on definitions

Shah A. A.^1,*, Batmanathan Navakanesh²

1 Department of Physical and Geological Sciences, University of Brunei Darussalam, Brunei
2 Southeast Asia Disaster Prevention Research Initiative, Universiti Kebangsaan Malaysia, Malaysia
*Corresponding author email address: afroz.shah@ubd.edu.bn

Abstract: The terms: Active tectonics and active faults have emerged as some of the most frequently used terms in geological literature, and traditionally, the main purpose of these definitions has historically remained devoted to either geological or engineering uses. However, most of the existing literature on the definitions has been gathered since >230 years that were spent on the understanding of the science of earthquakes, but a clear-cut consensus lacks on how to define active tectonics and active faults, for various reasons that are discussed at length here. Therefore, this paper presents a brief overview of the terms with a motivation to rekindle the discussion on what is considered active in tectonics. It also explores whether the traditional definitions are valid or not, and should we look for other alternatives. We present a brief historical background knowledge and understanding on the active faults, and particularly in some of the tectonically stable and presumably inactive portions of the Earth’s crust. The two major strike-slip faulting events (Mw 8.6 and Mw = 8.2) that have occurred in the Wharton Basin, Indian Ocean in 2012 are discussed in detail. The events are specially quoted to make a case for reactivation of old fracture systems as these earthquakes ruptured the ~30-90 Ma old Indian oceanic crust. This clearly demonstrates that much older geological structures could also be re-activated, thereby questioning the traditional definition of the typical time span that is used to define active tectonics and active faults.

Keywords: Active tectonics, active faults, earthquakes, Wharton Basin

DOI: https://doi.org/10.7186/bgsm70202010