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The aseismic Nazca Ridge produces localized flat-slab subduction beneath the South American margin at latitudes 10° to 15° S. The geological evolution and the spatio-temporal pattern of deformation of the upper plate have been strongly influenced by the presence of the flat slab. In this study, we investigated the lithospheric thermal structure of this region by elaborating a 2D geothermal model along a section across the top of the Nazca Ridge, the Peru–Chile trench, the Andean Cordillera, and the Amazonian Basin, for a total length of 1000 km. For the sake of modelling, the crust of the overriding plate was subdivided into two parts, i.e., a sedimentary cover (including the entire lithostratigraphic sequence) and a crystalline basement. Applying an analytical methodology, we calculated geotherms and isotherms by setting (i) thickness, (ii) density, (iii) heat production, and (iv) thermal conductivity for each geological unit and considering (v) heat flux at the Moho, (vi) frictional heating produced by faults, and (vii) plate convergence rate. The resulting model could make a significant advance in our understanding of how flat slab geometry associated with the Nazca Ridge subduction affects the thermal structure and hence the tectonic evolution of the region. [ABSTRACT FROM AUTHOR]

The 2010 Maule earthquake was a megathrust event that occurred along the Peru–Chile Trench. The earthquake source can be modelled as a fault with two asperities with different areas and strengths. By employing a discrete fault model, where asperities are the basic elements, the event can be described as a sequence of three dynamic modes involving simultaneous asperity slip. Interaction between asperities by mutual stress transfer plays a crucial role during fault slip. With a careful choice of values for the model parameters, the mode durations, the slip distribution, the seismic moment rate and the final moment calculated from the model are found to be consistent with the observed values. An important amount of frictional heat is produced by an event of this size and is calculated by summing up the contributions of each asperity. The seismic event produces a heat pulse propagating through the Earth's crust and contributing to the average heat flow in the region. The calculated heat production is equal to about 2 × 10 17 J and the peak value of the heat pulse is equal to 6 × 10 − 3 mW m − 2 or about 10 − 4 of the average surface heat flow density, with a characteristic diffusion time in the order of 10 6 a. [ABSTRACT FROM AUTHOR]

Using published cross-sections and a series of geological constraints, a 3D geological model of an important area of the Adriatic sector of peninsular Italy—i.e., the Marche region—was developed. Then, an analytical procedure, taking into account the heat rising from the mantle and the radiogenic heat produced by the crust, was applied on the pre-built structural model, in order to obtain the 3D geothermal setting of the entire region. The results highlighted the key role played by the Moho geometry, particularly as a step of ~10 km occurs between the Adriatic Moho of the subducting plate to the west and the new Tyrrhenian Moho characterizing the back-arc area to the west. The comparison between our results and available borehole data suggests a good fit between the applied analytical methodology and published datasets. A visible anomaly is located at a specific site (i.e., the coastal town of Senigallia), where it may be envisaged that fluid circulation produced a local surface heat flow increase; this makes the Senigallia area a promising feature for the possible exploitation of geothermal systems. [ABSTRACT FROM AUTHOR]

Using an analytical methodology taking into account heat flow density data, frictional heating, temperature variations due to the re-equilibrated conductive state after thrusting and geological constrains, we calculated surface heat flow, geotherms and isotherms along a balanced and restored regional geological cross-section. Our results highlight the impact of frictional heating produced by thrusts on the thermal structure of the study area, leading to a raising of the isotherms both in the inner Albanides to the E and in the Adriatic sector offshore. Minimum values of Q s in the surroundings of Tirana and the reconstructed 2D thermal structure suggest less favorable conditions for exploitation of geothermal energy, besides the direct use (Borehole Heat Exchanger-Geothermal Heat Pump systems). Nevertheless, the occurrence of the "Kruja geothermal zone", partially overlapping this area and including hot spring manifestations, emphasize the structural control in driving hot fluids to the surface with respect to the regional thermal structure. [ABSTRACT FROM AUTHOR]

The Zagros thrust belt is a large orogenic zone located along the southwest region of Iran. To obtain a better knowledge of this important mountain chain, we elaborated the first 3-D model reproducing the thermal structure of its northwestern part, i.e., the Lurestan arc. This study is based on a 3-D structural model obtained using published geological sections and available information on the depth of the Moho discontinuity. The analytical calculation procedure took into account the temperature variation due to: (1) The re-equilibrated conductive state after thrusting, (2) frictional heating, (3) heat flow density data, and (4) a series of geologically derived constraints. Both geotherms and isotherms were obtained using this analytical methodology. The results pointed out the fundamental control exerted by the main basement fault of the region, i.e., the Main Frontal Thrust (MFT), in governing the thermal structure of the crust, the main parameter being represented by the amount of basement thickening produced by thrusting. This is manifested by more densely spaced isotherms moving from the southwestern foreland toward the inner parts of orogen, as well as in a lateral variation related with an along-strike change from a moderately dipping crustal ramp of the MFT to the NW to a gently dipping crustal ramp to the SE. The complex structural architecture, largely associated with late-stage (Pliocene) thick-skinned thrusting, results in a zone of relatively high geothermal gradient in the easternmost part of the study area. Our thermal model of a large crustal volume, besides providing new insights into the geodynamic processes affecting a major salient of the Zagros thrust belt, may have important implications for seismotectonic analysis in an area recently affected by a Mw = 7.3 earthquake, as well as for geothermal/hydrocarbon exploration in the highly perspective Lurestan region. [ABSTRACT FROM AUTHOR]