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

Abstract

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