New insights on speleoseismology: The geothermal gradient and heat flow values in caves for the study of active faults. (7th September 2017)

• Record Type: Journal Article
• Authors: Pérez-López, R.; Martín-Velázquez, S.; Sánchez-Moral, S.; Patyniak, M.; López-Gutiérrez, J.; Cuezva, S.; Lario, J.; Silva, P.G.; Rodríguez-Pascua, M.A.; Giner-Robles, J.L.
• Is Part Of: Quaternary international. Volume 451(2017)
• Page Start: 165
• Page End: 175
• Publication Date: 2017-09-07
• Subjects: Speleoseismology -- Active fault -- Cave -- Slip-rate -- Heat flux; Geology, Stratigraphic -- Quaternary -- Periodicals; Stratigraphie -- Quaternaire -- Périodiques; 551.79
• DOI: 10.1016/j.quaint.2016.11.026
• Languages: English
• ISSNs: 1040-6182

Abstract

Abstract: Normally in paleoseismology, the study of the tectonic slip-rate is performed in trenches on the fault scarp, or by the estimation of fault movements from the geomorphic features. In this work, we have carried out a paleoseismic analysis of the Benis Fault, located in southeast Spain, combined with a geothermal analysis inside a deep cave related to the fault (−350 m). Thus, we have estimated the last earthquake magnitude and time of occurrence from evidence of ceiling collapse and displaced carbonate blocks inside a cave, which is developed across the fault. The magnitude was obtained from the application of the empirical relationship of the fault parameters and coseismic vertical displacement, yielding a value ranging between M 5.9 and M 6.5. Moreover, we dated this paleoearthquake by the paleontological record of a "Lynx pardinus spelaea", with an age of 65 ± 18 ka BP. Additionally, we have measured the thermal profile of the Benis Cave (−350 m of depth), from single rock point temperature measurements during 2 years. The temperature profile shows three different parts inside the cave, the shallow heterogeneous thermal zone till 50 m depth; the homogeneous thermal zone 150 m till with constant temperature and the hetero-thermal deep zone, deeper than 150 m and till the deepest zone (350 m). Furthermore, we have estimated the Vertical Geothermal Gradient, 1.85 °C/100 m for the deepest zone (−150; −290 m). The temperature increases with depth, showing a reverse thermal profile in comparison with normal gradients in deep caves. Finally, we have calculated the heat flux of 0.46 mWm 2 .