We use freely available Google satellite data, instrumental seismicity, fault plane solutions, and previously mapped structural and geological maps to identify new fault zones in central Borneo.We have mapped a number of~NW-SE trending dextral strike-slip faults and~NE-SW to~N-S trending sinistral strike-slip fault zones. The geomorphic expression of faulting is shown by the well-developed triangular facets, fault rupture scarps, truncated sedimentary beds, topographic breaks, displaced ridges, deflected streams, faulted Plio-Pleistocene volcanic deposits, and back-tilted Holocene to Recent sedimentary deposits. Some of the mapped faults are actively growing, and show text-book examples of dextral and sinistral offset, which ranges from~450 m to tens of km. The dextral strike-slip fault systems are clearly developed in the central and eastern portions of Borneo where they cut through the folded sedimentary sequences for >220 km. The~NE-SW tõ N-S trending sinistral strike-slip faults are dominantly developed in the eastern portion of central Borneo for >230 km. The geomorphic expression of faulting is clear and the fault scarps are~SE facing for the sinistral fault system, and~NE facing for the dextral fault system. The age of the faulting is constrained by the cross-cutting relationship where the fault cuts through Plio-Pleistocene volcanic deposits for >30 km, which suggests a neotectonic nature of faulting. The strike-slip fault systems that we have mapped here provide the first geomorphic evidence of large-scale strike-slip faulting in Borneo and suggest the presence of a major sinistral strike-slip fault that runs for >900 km through the center of Borneo, and forms a backbone onto which most of the mapped structures root. The mapped structures clearly suggest that plate tectonic forces dominantly control the geological structures that we have mapped and support the regional oblique convergence that is oblique with respect to the major trend of the Crocker Range, which forms the spine of the Borneo Island.
Unscientific, false, inaccurate and/or exaggerated reporting about anything in media or other platforms is a serious concern that needs a solution. This is particularly important when reporting about disasters (e.g., earthquakes). The lack of authentic scientific input into about science news reporting may can lead to news disasters, which may can prove to be much more critical and dangerous than say-earthquake disasters. Therefore, this paper explores such a this problem in a portion of NW Borneo and offers solution to improve the existing norms on the earthquake science, education and awareness programs in SE Asia. The explored field location is Sabah, Malaysia, which is targeted to map the level of earthquake science education and awareness of local people, and to examine the co-seismic deformation associated with the 5th June, 2015 earthquake. This event has surprised the local communities because the region is geographically located away from the active tectonic plate boundaries, and has traditionally been considered a low earthquake risk region. This is in contrast to the existence of high earthquake hazard and risk regions in the neighboring Indonesia and the Philippines. Therefore, not surprisingly, the residents of Borneo where puzzled, surprised, and worried when a medium magnitude earthquake occurred and caused significant loss of life and property. The lack of scientific education on the causes, and remedies of earthquake hazards in most of the South and Southeast Asian regions is a reality, which needs a proper solution. Therefore, through this work a small initiative has been started in Sabah, Malaysia where stories from the earthquake victims were recorded after the devastation caused by the June 2015 earthquake. Their real time experiences were blended with the updated scientific data on the occurrence of earthquakes in Borneo, which are mostly gathered from previously published works and the work presented here. The entire work is converted into a small documentary movie that highlights the causes of earthquakes and how it impacts human life.
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.
The western Himalayan syntaxis represents the region where the major Himalayan structures abruptly curve and the cause of the curvature and the tectonic geomorphology of the region has not been fully explored. The lack of detailed structural maps with extensive field-based data is missing, which is mainly because of the political problems related to border sharing between Pakistan, India, and Afghanistan. However, and fortunately, the usage of satellite-derived images has overcome such constraints by providing a robust platform to remotely map such regions. Therefore, the present study was aimed to supplement our previous works in the region by exploring the western portions of the Hazara-Kashmir-Syntaxis. We have used Google Terrain imagery to map the evidence for active faulting that involves mapping of triangular facets, displaced and/or faulted topographic ridges, river terraces, alluvial fans and so on. The cross-cutting relationships are used to date the faulting events where absolute dates are not available. Our results show that active tectonic deformation is not just limited to the previously mapped structures (e.g. the Kalabagh Fault, the Salt Range Thrust, the Mahesian Anticline, and the Jhelum Fault) but occurs on a broader deformation zone that is delimited by the Chaman fault system in the west, and the Jhelum fault in the east. The deformation zone in 3D resembles a tectonically formed diamond-shaped box that has the Salt-Range thrust in front and the Main boundary thrust fault at the back with sides delimited by the Chaman and the Jhelum fault systems. The earthquake centroid moment tensor data complements our geomorphological work and establishes that transpression is a dominant tectonic process that governs the western regions, which is in comparison to the east where transtension is the norm in the interior Himalayan with reverse and thrust faulting dominant in the frontal regions.
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