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 to ~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.
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