Geophysics
The geothermal gradient was measured at a gas seep in Smithton as 26.4 degrees/km. Forest has 27.8 °/km. The Otway Basin has a gradient of 36°/km. Several companies are exploring for hot rocks for geothermal energy. The granite areas have a gradient of 30°/km, whereas the Parmeener sedimentary areas have a gradient of 40°/km. Heat flow is between 85 and 159 mW/m2.
Active seismic exploration reveals the nature of the deep crust. It shows that the Tyennan block plumbs the depth to the moho which is about 33 km underneath. The Tyennan Block slopes below the Adamsfield-Jubilee Element. Under the Tasmania Basin the block is stretched, with faults in to several large blocks that have tilted down. Above these the Adamsfield-Jubilee Element sediments have filled in the topography. Below the north east element the moho is 36 km deep with alternating seismically fast and slow rocks in the mid crust. The Tyennan Block and the Rocky Cape Element have a boundary that dips at 30D to the east to the base of the crust. The Dundas Element lies on top of this boundary. A shallower Moho occurs under the Rocky Cape Block at 26 to 28 km. A deep segment is found under the central north of the state, down to 34 km. Bass Strait is a low seismic velocity zone.
Magnetic field measurements show that the different elements making up Tasmania have very different signatures. Wherever there is Jurassic Dolerite, the magnetic map shows fine ripples, so the Tasmania Basin stands out, as does the smaller intrusions in the other elements. The North east element is smooth, as is the Tyennan Block, and the Adamsfield-Jubilee Element. The Dundas Element has a smooth background with prominent north-south ridges. The Rocky Cape Element is densely packed with linear textures parallel to the Arthur Lineament, with the Smithton Syncline showing as a Y shape. King Island also shows north-south texture. Basalt south of Wynyard also shows a wrinkly magnetic signature.
The stress field in the crust has not yet been measured.
Read more about this topic: Geology Of Tasmania