90 research outputs found
Discovering the characteristics of the surface faulting ancestors of the L’Aquila April 6, 2009 earthquake by paleoseismological investigations
The occurrence of the Mw 6.3, April 6, 2009 earthquake has highlighted how critical is the development of hazard
models that incorporate all the information on the long-term seismic behavior of faults (i.e., individual events
rupture length and slip, timing, etc.). Under this light we started a campaign of paleoseismological investigations
in the epicentral area.
The 2009 earthquake occurred on the Paganica normal fault (PF hereinafter) and produced a max 0.15 m
high, 3 km-long continuous surface rupture along its central section, as well as several short, discontinuous cracks
along the rest of the fault trace; secondary slip along nearby tectonic structures was observed too.
The PF consists of a prominent NW-SE striking and SW dipping long-term morphologic scarp formed by
the tectonic juxtaposition of Pliocene-middle Pleistocene and late Pleistocene alluvial deposits, and by smaller
compound scarps in late Pleistocene-Holocene deposits. The fault runs for a total length of about 20 km along the
NE side of the Aterno River valley, a graben-type basin bounded by marked antithetic faults.
The limited extent and the small throw of the 2009 surface ruptures, when compared to the size of the Paganica
long-term fault scarp, raise questions about the evolution and rupture history of this fault and suggest that
the PF may have experienced larger Magnitude earthquakes than the 2009 seismic event.
With the aim of defining the Max Magnitude expected for the PF by determining the size of the individual
coseismic surface ruptures occurred in the past and their max extent, their frequency and the average rate of
displacement we have been excavating new trenches and studied artificial exposures across the PF fault zone, in
most of the cases intersecting the 2009 surface ruptures.
Preliminary results show evidence for repeated decimetric surface faulting events during the past 3 millennia
with the penultimate likely being the 1461 event (Me 6.4); evidence for possible previous larger slip events
is found too. Whether the small ruptures are all related to slip at depth on the PF or would represent sympathetic
slip triggered by earthquake occurred on nearby faults should be better investigated. Conversely, provided the
“double size” slip behavior of the PF is confirmed, to characterize the seismic hazard of the area we should
consider a more complex seismogenic model than that presently applied. In particular, we should include also the
scenario that the PF produces relatively frequent (each 4-600 yr) 2009-type earthquakes and rare (each 3-4 millennia)
larger events, likely in connection with other nearby active structures (i.e., San Demetrio Fault? Pettino Fault?)
Looking for seismites in the Fucino basin: preliminary results from a combined geological geophysical approach.
We present a combined geological-geophysical study on the lacustrine sequence of the Fucino Plain (central Italy). New
acquired data on liquefaction features and the recovery of a seismite in the lacustrine sequence are shown. Our preliminary
results suggest the occurrence of three seismic events in the last ca. 45 kyr. Moreover, a first attempt to find out the source deposit
responsible of the widespread liquefaction phenomena has been performed by means of shallow engine boreholes and ERT
profiles
Long-term expression of the Paganica Fault vs. 2009 L’Aquila Earthquake surface ruptures: looking for a better understanding of its seismic behavior
The Mw6.3, April 6, 2009 earthquake occurred on the previously identified Paganica normal fault and produced
a 3 km-long co-seismic surface rupture along its northern section, with few centimeters of vertical displacement.
Extensive 1:10,000-scale geological and geomorphological mapping has been carried out, focusing on the
characterization of the long-term expression of the Paganica Fault at the surface. The field mapping was integrated
by observations, made on 1:33,000 scale aerial photographs (GAI), 5-m-resolution Digital Elevation Model and
standard morphometric derivatives (hill-shaded and slope angle maps, Spatial Analyst™). Particular attention
was devoted to the study of the continental deposits and landforms affected by cumulative offset with the aim to
reconstruct the Quaternary deformational history of the fault. The fault runs for a total length of 20 km and, along
with antithetic faults on its hanging-wall, forms the graben of the Middle Aterno River Valley. The whole fault
system and the variable setting of deformation affecting the continental deposits at the surface were identified.
The Paganica long-term morphologic signature is represented by a set of prominent scarps formed by the tectonic
juxtaposition of late Pliocene-middle Pleistocene and late Pleistocene alluvial deposits, and by lower scarps in
late Pleistocene-Holocene deposits. In addition, evident Quaternary erosional and depositional paleosurfaces were
recognized and sampled for 14C and OSL (Optically Stimulated Luminescence) and tephra chronology dating for
long-term slip-rate calculations.
This study resulted helpful to locate four paleoseismological investigations (see Pantosti et al. talk) and to provide
the appropriate context for correctly interpret the depositional bodies outcropping on the trench walls. These
paleoseismological investigations evidenced the presence of repeated late Pleistocene-Holocene activity and
allowed for slip-rate estimation at a shorter time-scale. Such estimates were valuable for a comparison with the
preliminary estimates on late Pleistocene calculations carried out by geomorphological investigations.
Moreover, we correlated co-seismic deformations with the long-term morphologies and structures. The 2009
co-seismic ruptures show a general coherence with the long-term Paganica fault trace, both in terms of location
and style. However, the limited extent of the 2009 surface ruptures coincides with the portion of the fault
trace where deformation is more localized and few splays contribute to the extension. This is also testified by
the presence on its hanging-wall of a large late Pleistocene-Holocene alluvial fan that subsides over the basin
depocenter. Conversely, where the Paganica fault system branches out, various splays accommodated the small
2009 co-seismic throw, resulting in a distributed and not evident extensional strain.
The preserved fault-related geomorphology is evidence for the persistence of the rupture complexities during
Quaternary. On this light, further studies on the style of fault activity are needed to estimate if the Paganica fault
is capable of earthquakes with Magnitude larger than the 2009 event.SubmittedVienna, Austriaope
Reply to “Comment on ‘The 21 August 2017 Md 4.0 Casamicciola Earthquake: First Evidence of Coseismic Normal Surface Faulting at the Ischia Volcanic Island’ by Nappi et al. (2018)” by V. De Novellis, S. Carlino, R. Castaldo, A. Tramelli, C. De Luca, N. A. Pino, S. Pepe, V. Convertito, I. Zinno, P. De Martino, M. Bonano, F. Giudicepietro, F. Casu, G. Macedonio, M. Manunta, M. Manzo, G. Solaro, P. Tizzani, G. Zeni, and R. Lanari
In this article, we show why the geological model of the 21 August
2017 earthquake proposed by Nappi et al. (2018) has less
uncertainty than the sourcemodel proposed by De Novellis et al.
(2018). As a matter of fact, the Nappi et al. (2018) model takes
into account all geophysical and geological information collected
soon after the earthquake. On the contrary, the model proposed
by DeNovellis et al. (2018) is based on a limited database, which
does not include (1) the available geological and macroseismic
information and (2) the extensive scientific literature concerning
the correlation between seismic source and surface faulting, also
in volcanic areas similar to Ischia.
Nevertheless, we are grateful for the comments from De Novellis
et al. (2018) because they give us the opportunity to consider
the epistemological landscape in which we should frame
the research for the best source model of the 21 August 2017
Casamicciola earthquake.Published316-3211T. Deformazione crostale attivaJCR Journa
Liquefied sites of the 2012 Emilia earthquake: a comprehensive database of the geological and geotechnical features (Quaternary alluvial Po plain, Italy)
This paper presents a comprehensive geological and geotechnical study of the whole area affected by liquefaction following the 2012 Emilia earthquakes, including all the available information from the field reconnaissance surveys, in situ tests, and laboratory analyses. The compilation was performed at 120 liquefied sites to verify and validate the reliability of liquefaction charts in alluvial sediments, and to assess liquefaction induced by the 2012 seismic sequence in the Emilia plain. The results reveal a wide range of grain sizes (from clean sands to sandy silts) and compositional characteristics (quartz-rich to litharenitic) in the 2012 ejecta, and show a strong relationship between the liquefaction and stratigraphic architecture of the subsurface. The availability of in situ tests at the liquefied sites makes it possible to verify and validate the reliability of the liquefaction charts in alluvial sediments with respect to the real observations. For the analyzed Emilia case studies, the use of non-liquefiable crust provides better estimations of the liquefaction manifestations when coupled with the thickness of the liquefiable layer rather than with the liquefaction potential index. Altogether, this work makes available to the international scientific community a consistent liquefaction database for in-depth earthquake studies
Imaging the structural style of an active normal fault through multidisciplinary geophysical investigation: a case study from the Mw 6.1, 2009 L'Aquila earthquake region (central Italy)
The normal fault-system responsible of the 2009 Mw 6.1 L'Aquila earthquake (Paganica-San Demetrio fault-system) comprises several narrow, fault-parallel valleys of controversial origin. We investigated a key section of the southeastern portion of this fault network along the small Verupola Valley. In order to characterize its nature and possible tectonic activity, we applied multiple-geosciences techniques able to image at depth the structure associated to this peculiar landform. We integrated magnetometry, 2-D P wave and resistivity tomography, surface waves and seismic noise analysis coupled with field mapping, shallow boreholes and trenching. According to our results, the Verupola Valley is a ∼30–40-m-deep graben controlled by a SW-dipping master fault and synthetic splays paired with an antithetic NE-dipping fault. The SW-dipping splays are active and cut very shallow (<2 m deep) Late Pleistocene sediments. The small amount of cumulated vertical offset (∼15 m) across the conjugated system may indicate a young fault inception or very low Quaternary slip-rates. Due to its structural continuity with the adjacent mapped strands of the Paganica–San Demetrio fault network, we relate the Verupola Valley to the recent activity of the southeastern segment of this fault system. We also suggest that other fault-parallel valleys can have the same tectonic origin and setting of the Verupola Valley. This latter represents a scale-independent analogue from metric scale (exposed in the palaeoseismological trenches) to the Middle Aterno Basin scale (seen from seismic profiles and fault mapping). Overall, the imaged structural style is coherent with the regional tectonic setting due to Quaternary crustal extension
Detecting young, slow‐slipping active faults by geologic and multidisciplinary high‐resolution geophysical investigations: A case study from the Apennine seismic belt, Italy.
The Southern Apennines range of Italy presents significant challenges for active fault detection due to the complex structural setting inherited from previous contractional tectonics, coupled to very recent (Middle Pleistocene) onset and slow slip rates of active normal faults. As shown by the Irpinia Fault, source of a M6.9 earthquake in 1980, major faults might have small cumulative deformation and subtle geomorphic expression. A multidisciplinary study including morphological-tectonic, paleoseismological, and geophysical investigations has been carried out across the extensional Monte Aquila Fault, a poorly known structure that, similarly to the Irpinia Fault, runs across a ridge and is weakly expressed at the surface by small scarps/warps. The joint application of shallow reflection profiling, seismic and electrical resistivity tomography, and physical logging of cored sediments has proved crucial for proper fault detection because performance of each technique was markedly different and very dependent on local geologic conditions. Geophysical data clearly (1) image a fault zone beneath suspected warps, (2) constrain the cumulative vertical slip to only 25–30 m, (3) delineate colluvial packages suggesting coseismic surface faulting episodes. Paleoseismological investigations document at least three deformation events during the very Late Pleistocene (<20 ka) and Holocene. The clue to surface-rupturing episodes, together with the fault dimension inferred by geological mapping and microseismicity distribution, suggest a seismogenic potential of M6.3. Our study provides the second documentation of a major active fault in southern Italy that, as the Irpinia Fault, does not bound a large intermontane basin, but it is nested within the mountain range, weakly modifying the landscape. This demonstrates that standard geomorphological approaches are insufficient to define a proper framework of active faults in this region. More in general, our applications have wide methodological implications for shallow imaging in complex terrains because they clearly illustrate the benefits of combining electrical resistivity and seismic techniques. The proposed multidisciplinary methodology can be effective in regions characterized by young and/or slow slipping active faults.PublishedB113073.2. Tettonica attivaJCR Journalpartially_ope
Imaging the three-dimensional architecture of the Middle Aterno basin (2009 L’Aquila earthquake, Central Italy) using ground TDEM and seismic noise surveys: preliminary results
We present preliminary results from a multidisciplinary geophysical approach applied to the imaging of the threedimensional
architecture of the Middle Aterno basin, close to the epicentral area of the 2009 L’Aquila earthquake (central Italy).
We collected several time domain electromagnetic soundings (TDEM) coupled with seismic noise measurements focusing on the
characterization of the bedrock/infill interface. Our preliminary results agree with existing geophysical data collected in the area,
and show that the southeastern portion of the basin is characterized by a deepening of the Mesozoic-Tertiary bedrock down to a
depth of more than 450 m. We found that a joint use of electromagnetic and seismic methods significantly contributes in
obtaining new insights on the 3D geometry of the Middle Aterno basin. Moreover, we believe that our combined approach based
on TDEM and noise measurements can be adopted to investigate similar geological settings elsewhere.PublishedPescina (AQ)2T. Tettonica attivaope
Imaging the three-dimensional architecture of the Middle Aterno basin (2009 L’ Aquila earthquake, Central Italy) using ground TDEM and seismic noise surveys: preliminary results
We present preliminary results from a multidisciplinary geophysical approach ap- plied to the imaging of the three-dimensional architecture of the Middle Aterno basin, close to the epicentral area of the 2009 L’Aquila earthquake (central Italy). We collected several time domain electromagnetic soundings (TDEM) coupled with seismic noise measurements focu- sing on the characterization of the bedrock/in ll interface. Our preliminary results agree with existing geophysical data collected in the area, and show that the southeastern portion of the basin is characterized by a deepening of the Mesozoic-Tertiary bedrock down to a depth of more than 450 m. We found that a joint use of electromagnetic and seismic methods signi - cantly contributes in obtaining new insights on the 3D geometry of the Middle Aterno basin. Moreover, we believe that our combined approach based on TDEM and noise measurements can be adopted to investigate similar geological settings elsewhere.PublishedPescina (AQ), Italy2T. Tettonica attiva3T. Pericolosità sismica e contributo alla definizione del rischio7A. Geofisica di esplorazioneope
Imaging the three-dimensional architecture of the Middle Aterno basin (2009 L’Aquila earthquake, Central Italy) using ground TDEM and seismic noise surveys: preliminary results
We present preliminary results from a multidisciplinary geophysical approach applied to the imaging of the threedimensional
architecture of the Middle Aterno basin, close to the epicentral area of the 2009 L’Aquila earthquake (central Italy).
We collected several time domain electromagnetic soundings (TDEM) coupled with seismic noise measurements focusing on the
characterization of the bedrock/infill interface. Our preliminary results agree with existing geophysical data collected in the area,
and show that the southeastern portion of the basin is characterized by a deepening of the Mesozoic-Tertiary bedrock down to a
depth of more than 450 m. We found that a joint use of electromagnetic and seismic methods significantly contributes in
obtaining new insights on the 3D geometry of the Middle Aterno basin. Moreover, we believe that our combined approach based
on TDEM and noise measurements can be adopted to investigate similar geological settings elsewhere
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