Investigating the deep structure of terranes and terrane boundaries: insights from earthquake seismic data

Abstract

The crust and upper mantle structure beneath a single, three-component broadband seismic station may be determined using cnergy from distant earthquakes. Features such as the depth of the seismic Moho, the abruptness of the change in seismic velocity across the Moho. the velocity profile through the crust and the seismic velocity of the upper mantle may be found using receiver function teehniques. Waveforms are analysed which contain energy arising from the interaction 01 incoming signals with the Earth structure beneath the receiving station. Seismic characteristies of the deep crust are olten continuous or slowly varying across a single tcrrane and. moreover. show sudden contrasts aeross tcrrane and other major tectonic boundaries. Such techniques are, therefore, appropriate tools in the exploration of deep structure and. henee, in the understanding of large-seale eontinentalassembly. They complement geologieal and geochronologieal investigations of surface rocks by providing the (hird spatiai dimension. In regions of no surface basemcnt exposure, scismic and other gcophysieal methods provide the only means of mapping the lateral extent of a given terrane and/or tracing province boundaries. Receiver function methods are presented here in the context of terrane tectonics with illustrative examples from former Gondwanan provinees and locations on the Pacific margin.