the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Paleoseismological evidence of multiple, large magnitude earthquake surface ruptures on the active Mt. Morrone normal fault, central Apennines, Italy
Abstract. The Mt. Morrone active normal Fault (MMF) and the related Sulmona intermountain basin constitute one of the most characteristic examples of the extensional tectonic landscape carving the central Apennines (Italy). Above the ⁓22 km MMF, thousands of inhabitants concentrate on a thriving reality and a historical and cultural heritage of great significance. According to the current knowledge, the last activation event of the whole MMF occurred ⁓2000 years ago and the maximum expected magnitude is M 6.6–7. Thus, the MMF today constitutes one of the most problematic structures in the central Apennines seismotectonic setting in terms of large-magnitude earthquake probability. Despite this, information on the activity of the MMF is presently relatively few, both for associated historical seismicity and paleoseismological data. To strengthen these knowledge weaknesses, we performed new extensive paleoseismological analyses (employing four trenches) in the central sector of the fault. Our goal was to supplement the limited existing dataset, constituted by a single paleoseismological study close to the northwestern tip of the fault. Additionally, we aimed to incorporate findings from a pair of studies focused on archaeoseismological and speleoseismological secondary evidence. Through these analyses, we unveiled four significant surface rupture events of the MMF, three of which occurred over the past 6000 years BP. Specifically, the youngest identified event occurred after 3.6–3.5 kyr BP, being thus chronologically consistent with the event in 2nd century CE; a penultimate event after 4.4 kyrs BP; a previous event occurred after 5.4–5.3 kyr BP; and the oldest event took place after 9–8.9 kyr and (presumably) before 5.8–5.7 kyr BP. Considering that the cumulative minimum vertical displacement estimated encompassing the last three events is ⁓140 cm, and based on the length of the fault at the surface, we can confirm that earthquakes with M 6.6–7.0 may be expected from the activation of the MMF with an inferred average recurrence interval not longer than 1800 years over the last ⁓5.4 kyr.
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RC1: 'Comment on egusphere-2024-2399', Francesco Iezzi, 09 Oct 2024
The authors present a thorough paleoseismological investigation on the Mt Morrone fault, Central Italy. Their work allow for the identification of multiple surface-rupturing earthquakes occured during the Holocene, expanding therefore the available seismic record of the fault. Data presented in this paper would have a sensible impact on seismic hazard assessments of the region, unveiling the seismic behaviour of one of the major active faults located in a populated region.
I find the manuscript clear and of a good quality. I attach a PDF with minor comments and clarifications required prior to publication.
Thank you.
Regards
Francesco Iezzi
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RC2: 'Comment on egusphere-2024-2399_Nasim Mozafari', Nasim Mozafari Amiri, 24 Oct 2024
The authors conduct a comprehensive study of the Mt. Morrone fault in central Italy by digging four paleoseismological trenches in the central sector of the fault. The results are valuable and highlight multiple surface-rupturing earthquakes that took place during the Holocene, thus improving the current seismic record for this fault. The findings presented in this paper have significant implications for seismic hazard assessments, providing insights into the seismic behavior of one of the major active faults situated in the seismic-prone region of central Apennines.
Nonetheless, I feel that a few minor adjustments are required to improve clarity. These modifications do not challenge the scientific validity of the study; rather, they aim to clarify certain aspects. As a general comment, the authors submitted their samples for radiocarbon dating to two different laboratories; however, they only reported results from one lab for each sample. They should clarify how they determined which age estimate is more accurate. I have also attached an annotated PDF for the authors' consideration of minor revisions.
I look forward to reading the revised version of the manuscript.
Regards,
Nasim Mozafari
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