Fracture lineaments, fault mesh formation and seismicity
Towards a seismotectonic model for Viti Levu, Fiji
Viti Levu, the main island of Fiji, is located in a seismically active area within the Fiji Platform, a remnant island arc that lies in a diffuse plate boundary zone between the Pacific and Australian tectonic plates in the SW Pacific. The upper crust of Viti Levu is dissected by numerous intersecting fault/lineament zones mapped from remote sensing imagery of the land surface (topography, radar and aerial photos) and basement (magnetic) and have been subject to rigorous statistical tests of reproducibility and verification with field mapped fault data. Lineaments on the various imagery correlate with faults mapped in the field, and show spatial continuity between and beyond mapped faults, thereby providing a fuller coverage of regional structural patterns than previously known. Some fault/lineaments zones extend beyond the coastline to the offshore area from the SE Viti Levu study area. Multibeam bathymetry and seismic reflection data show the fault zones occur along and exert control on the location of a number of submarine canyons on the SE slope of Viti Levu. Evidence for Late Quaternary fault activity is only rarely observed in onshore SE Viti Levu (e.g. by displaced shoreline features), and in seismic reflection profiles from offshore.
The principal fault sets in Viti Levu represent generations of regional tectonic faulting that pervade the Fiji Platform during and after the disruption of the proto Fijian arc in the Middle to Late Miocene (~15Ma). These fault sets combine to form a complex network of interlocking faults creating a fault mesh that divides the upper crust into a number of fault blocks ranging from ~2-30 km wide. It is inferred that the fault mesh evolved throughout the Neogene as a response to the anticlockwise rotation of the Fiji Platform through progressive development of different fault sets and intervening crustal block rotations. Regional tectonic deformation is presently accommodated in a distributed manner through the entire fault mesh. Low magnitude earthquakes (<M4) occur regularly and may represent ruptures along short linking segments of the fault mesh, while infrequent larger earthquakes (>M4) may result from complex rupture propagation through several linking fault segments of the mesh that lie close to optimum stress orientations. The interpreted model of distributed deformation through the fault mesh for the study area in SE Viti Levu is inferred to be characteristic of the style of active deformation that occurs throughout the entire Fiji Platform.
Reiter, L. (1990). “Earthquake Hazard Analysis: Issues and Insights”. Columbia University Press, NY, 254p.
Hamburger, M.W., Everingham, I.B., Isacks, B.L. and Barazangi, M. (1988). “Active tectonism within the Fiji platform, southwest Pacific”. Geology 16, 237 -241. DOI: https://doi.org/10.1130/0091-7613(1988)016<0237:ATWTFP>2.3.CO;2
Rodda, P. (1992). “Geological observations around Kabu, Bau”. Fiji Mineral Resources Department Note BP/102. 6p.
Shorten, P. (1993). “The geological and tectonic setting for ground failure hazards in Suva Harbour and environs”. Fiji Mineral Resources Department Memoir 3: 105p.
Rahiman, T.I.H. (2006). “Neotectonics, seismic and Tsunami hazards, Viti Levu, Fiji”. PhD thesis, University of Canterbury Library, Christchurch, New Zealand. 326p.
Rahiman, T.I.H. and Pettinga, J.R. (2008). “Analysis of lineaments and their relationship to Neogene fracturing, SE Viti Levu, Fiji”. Geological Society of America Bulletin; doi:10.1130/B26264.1; Data Repository item 2008164.
Smith, R. & Raicebe, T. (comps.) (1984). “Bathymetric map of Fiji”, Fiji Mineral Resources Department.
Brocher, T.M. and Holmes, R. (1985). “The marine geology of sedimentary basins south of Viti Levu, Fiji”. In: Investigations of the Northern Melanesian Borderland, Circum-Pacific Council for Energy and Mineral Resources, Earth Science Series 3: 123-138.
Hamburger, M.W., Everingham, I.B., Isacks, B.L. and Barazangi, M. (1990). “Seismicity and crustal structure of the Fiji Platform, southwest Pacific”. Journal of Geophysical Research 95: 2553-2573.
Boyer, R. and McQueen, J. (1964). “Comparison of mapped rocks fractures and airphoto linear features”. Photogrammetric Engineering and Remote Sensing 30: 630-635.
O'Leary, D.W., Friedman, J.D. and Pohn, H.A. (1976). “Lineament, linear, lineation; some proposed new standards for old terms”. Geological Society of America Bull. 87: 1463-1469.
Braun, O.P.G. (1982). “A structural analysis of Brazil, based on the study of major lineaments derived from remote sensing imagery”. Photogrammetria 37: 77-108.
Wise, D.U., Funiciello, R., Parotto, M. and Salvini, F. (1985). “Topographic lineament swarms; clues to their origin from domain analysis of Italy”. Geological Society of America Bulletin 96: 952-967.
Cortes, A.L., Maestro, A., Soriano, M.A. and Casas, A.M. (1998). “Lineaments and fracturing in the Neogene rocks of the Almazan Basin, northern Spain”. Geol. Magazine 135: 255-268.
Roy, D.W., Schmitt, L., Woussen, G. and DuBerger, R. (1993). “Lineaments from airborne SAR images and the 1988 Saguenay earthquake, Quebec, Canada”. Photogrammetric Engineering and Remote Sensing 59: 1299-1305.
Rahiman, T.I.H. and Pettinga, J.R. (2006). “The offshore morpho-structure and tsunami sources of the Viti Levu Seismic Zone, SE Viti Levu, Fiji”. Marine Geology 232: 203-225.
Nicholson, C. and Seeber, L. (1989). “Evidence for Contemporary Block Rotation in Strike-slip Environments: Examples from the San Andreas Fault System, Southern California. In: C. Kissel and C. Laj (eds.) Paleomagnetic Rotations and Continental Deformation; Kluwer Academic Publishers: 247-280.
Jackson, J. & Molnar, P. 1990. “Active faulting and block rotations in the western Transverse Ranges, California”. Journal of Geophysical Research 95: 22,073-22,087.
Nur, A., Ron, H. and Scott, O. (1989). “Mechanics of distributed fault and block rotation”. In: Kissel, C. & Laj, C. eds. Paleomagnetic rotations and continental deformation, NATO ASI Series. Series C: Mathematical and Physical Sciences 254: 209-228.
Malahoff, A., Hammond, S.R., Naughton, J.J., Keeling, D.L. and Richmond, R.N. (1982). “Geophysical evidence for post - Miocene rotation of the island of Viti Levu, Fiji, and its relationship to the tectonic development of the North Fiji Basin”. Earth and Planetary Science Letters 57: 398-414.
Prichard, T.R. (1989). “Palaeomagnetism and tectonics of Fiji”. Masters Thesis, Department of Geology and Geophysics, University of Sydney, Sydney.
Inokuchi, H., Yaskawa, K. and Rodda, P.U. (1992). “Clockwise and anticlockwise rotation of Viti Levu, Fiji; in relation to the tectonic development of the North and the South Fiji Basin”. Geophysical Journal International 110, 225-237. DOI: https://doi.org/10.1111/j.1365-246X.1992.tb00869.x
Taylor, G.K., Gascoyne, J. and Colley, H. (2000). “Rapid rotation of Fiji; paleomagnetic evidence and tectonic implications”. Journal of Geophysical Research 105: 5771-5781.
Begg, G. and Gray, D.R. (2002). “Arc dynamics and tectonic history of Fiji based on stress and kinematic analysis of dikes and faults of the Tavua Volcano, Viti Levu Island, Fiji”. Tectonics 21, 14p. DOI: https://doi.org/10.1029/2000TC001259
Gunn, P.J., Mackey, T. and Meixner, A.J. (1998). “Interpretation of the results of the Fiji airborne geophysical survey project”. Report submitted by the Australian Geological Survey Organisation to AusAID as part of the Fiji Airborne Geophysical Survey Project, 36p.
Rodda, P. (1994). “Geology of Fiji. In: Stevenson, A.J., Herzer, R.H. & Ballance, P.F. eds. Contributions to the marine and on-land geology and resources of the Tonga - Lau-Fiji region”, SOPAC Technical Bulletin 8: 131-151.
Cluff, L.S., Hansen, W.R., Taylor, C.L., Weaver, K.D., Brogan, G.E., McClure, F.E., Idriss, I.M., Blayney, J.A. (1972). “Site evaluation in seismically active regions: an interdisciplinary team approach”. Proceedings First International Conference on Microzonation, Seattle, Washington, 2: 957-987.
Jones, T. (1998). “Probabilistic earthquake hazard assessment for Fiji”. Australian Geological Survey Organisation Record 1997/46.
Everingham, I.B. (1983b). “Reports of earthquakes felt in Fiji, 1850 – 1940”. Fiji Mineral Resources Department Report 48, 54p.
Houtz, R.E. (1962a). “The 1953 Suva earthquake and tsunami”. Bulletin of the Seismological Society of America 52: 1-12.
Houtz, R.E. (1962b). “Note on minor damage caused by the Suva earthquake of June 1961”. Bulletin of the Seismological Society of America 52: 13 -16.
Rahiman, T.I.H., Fong, I. and Vuetibau, L. (2001). “Preliminary assessment of earthquake damage west of Vatukoula, northern Viti Levu, Fiji”. Fiji Mineral Resources Dept Note BP79/09.
Everingham, I.B. (1983a). “Preliminary report on sesimic events in the Monasavu dam area”. Fiji Mineral Resources Department Note BP33/2, 14p.
Singh, A. (1996). “Seismic hazard assesment of a critical structure: the Monasavu Hydro-electric Dam, Fiji”. Masters thesis, RMIT, Melbourne.
Everingham, I.B. (1988). “Catalogue of felt earthquake reports in Fiji, 1941 – 1981”. Fiji Mineral Resources Department Report 64, 22p.
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