Seismic slip history of the Pizzalto fault (central Apennines, Italy) using in situ‐produced³⁶Cl cosmic ray exposure dating and rare earth element concentrations

Abstract

Morphological and geological observations reveal that most Apenninic faults are highly segmented and that the majority of the fault segments are less than 10 km long. Although these faults have undergone numerous paleoseismological investigations, quantitative data remain crucially lacking for a large number of fault segments. Because such data are essential to understanding how these faults have ruptured and interacted in the past and how they might behave in the future, we investigated the Holocene seismic history of the Pizzalto normal fault, a 13 km long fault segment belonging to the Pizzalto‐Rotella‐Aremogna fault system in the Apennines. We collected 44 samples from the Pizzalto fault plane exhumed during the Holocene and analyzed the 36Cl and rare earth element (REE) contents. Together, the 36Cl and REE concentrations show that at least six events have exhumed 4.4 m of the fault scarp between 3 and 1 ka, with slip per event values ranging from 0.3 to 1.2 m. No major events have been detected over the last 1 kyr. The Rotella‐Aremogna‐Pizzalto fault system has a clustered earthquake behavior with a mean recurrence time of 1.2 kyr and a low to moderate probability (ranging from 4% to 26%) of earthquake occurrence over the next 50 years.

Defining a mid-Holocene earthquake through speleoseismological and independent data: implications for the outer Central Apennines (Italy) seismotectonic framework

“…This is supported by paleoseismological investigations in trenches that allow for identification of the 4.6-4.8 kyr BP paleoearthquake along the Sulmona normal fault, in a time span comparable with the Rivisondoli (Calderoni et al, 1990;Brunamonte et al, 1991) and Aremogna paleoevents (D'Addezio et al, 2001). Moreover, Tesson et al (2016) recognized an event along the Pizzalto normal fault segment with an age (around 1.7-1.9 kyr) similar to the more recent 2nd century AD earthquake recorded along the Sulmona Fault (Galli et al, 2015). These paleoseismological data suggest that distinct fault segments of the Rotella-Aremogna fault system can be reactivated at different times and in different ways and that they can be repeatedly activated synchronously with the Sulmona normal fault (Fig.…”

“…Late Quaternary evidence of faulting have been described for the latter fault system (Pizzi et al, 2010), while paleoseismological studies allowed for four faulting events to be recognized in the past ∼ 9 kyr along the Sulmona Fault (Galli et al, 2015). Paleoearthquakes have also been identified along different segments of the Rotella-Aremogna normal fault system (Frezzotti and Giraudi, 1989;Calderoni et al, 1990;Brunamonte et al, 1991;D'Addezio et al, 2001;Tesson et al, 2016;Fig. 1).…”

“…7b; see Tesson et al, 2016, and references therein), located along the southeastern prosecution of the Sulmona Fault. Paleoseismological data collected along the Rivisondoli normal fault allowed for defining an earthquake post-dating the deposition of a paleosol dated 5415-5324/5585-5443 yr BP (2σ calibrated age interval obtained from the conversion of the A.…”

Schmidt hammer and terrestrial laser scanning (TLS) used to detect single‐event displacements on the Pleasant Valley fault (Nevada, USA)

“…The average single-event displacement (SED) estimated using the Schmidt hammer and TLS is 2.85 m at two transect sites and is roughly equivalent to the visually estimated 3 m. While this fault is an ideal case where we know some of the slip history, the results demonstrate that these techniques show promise for discriminating slip patches on larger carbonate fault scarps with longer paleoearthquake histories, and could be used alongside 36 Cl cosmogenic exposure-age dating to improve paleoseismic records on normal faults. On the Pleasant Valley fault in central Nevada, the documentation of a surface rupture in 1915, a long recurrence interval of faulting, slow weathering rate, and a relatively high (2-3 m) single-event displacement make the discrimination of the historical and penultimate slip patches unambiguous.…”

“…Relative-age dating techniques, based primarily on rock weathering, have been used alongside 36 Cl exposure-age dating of fault scarps to corroborate results and guide sampling for cosmogenic nuclide dating (Stewart, 1996;Zreda and Noller, 1998;Giaccio et al, 2003;Tucker et al, 2011;Wei et al, 2013;Wiatr et al, 2015;He et al, 2016;Tye and Stahl, 2018). These techniques work on the premise that slip patches previously exposed in earthquakes have been subjected to a longer duration of subaerial weathering than more recently exposed patches.…”