Refining seismic parameters in low seismicity areas by 3D trenching: The Alhama de Murcia fault, SE Iberia

Abstract

Three-dimensional paleoseismology in strike-slip faults with slip rates less than 1mm per year involves a great methodological challenge. We adapted 3D trenching to track buried channels offset by the Alhama de Murcia seismogenic left-lateral strike-slip fault (SE Iberia). A fault net slip of 0.9±0.1mm/yr was determined using statistical analysis of piercing lines for one buried channel, whose age is constrained between 15.2±1.1ka and 21.9–22.3calBP. This value is larger and more accurate than the previously published slip rates for this fault. The minimum number of five paleo-earthquakes identified since the deposition of dated layers suggests a maximum average recurrence interval of approximately 5ka. The combination of both seismic parameters yields a maximum slip per event between 5.3 and 6.3m. We show that accurately planned trenching strategies and data processing may be key to obtaining robust paleoseismic parameters in low seismicity areas.