--> Abstract: Seismic Modelling of Large-Scale Conical Intrusions; #90063 (2007)

Datapages, Inc.Print this page

Seismic Modelling of Large-Scale Conical Intrusions

 

Vigorito, Mario1, Andrew Hurst1, Anthony Stephen John Scott1, J. A. Cartwright2 (1) Aberdeen University, Aberdeen, United Kingdom (2) Cardiff University, Cardiff, United Kingdom

 

Seismic investigations documented that sand injections commonly show a conical morphology and occur either as isolated units or clusters of conical features. However despite of the great abundance of subsurface examples until now no analogue with a similar scale and geometry has been documented from outcrop. The Panoche Giant Injection Complex (CA, USA) is probably the largest injection complex occurring at outcrop. It extends for more than 54 km in length and it is up to 800m thick. This injection complex is characterised by the occurrence of winged sills and of low-angle dykes and dyke swarms, which are arranged to form injected units with a semi-elliptical to horse-shoe geometry in plan view and V- or U-shaped cross section. These features are 500 to 1.5km wide and in some cases cut vertically through more than 250 m of host rock. One of these injected units has been selected in order to perform seismic simulation. The selected unit is a 1.5km wide V-shaped, low-angle, asymmetric dyke. This latter is 15-18m thick and is characterised by two diverging inner segments which cut the host-rock strata with angles of 5-20º (total width 1.2 km) and pass outwards into more inclined segments 30-60º steep. A first attempt to model the acoustic response of this injected unit generated an asymmetric V-shaped seismogram, 75ms thick which closely match the dimension and geometry of conical features imaged from subsurface in the off-shore Shetland-Faroe and in the North Sea.

 

AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California