Present-day seismic activity in the Mugello Basin and adjoining areas (Northern Apennines, Italy)

2020 ◽  
Author(s):  
Rebecca Bruni ◽  
Giacomo Corti ◽  
Michele D'Ambrosio ◽  
Andrea Fiaschi ◽  
Carlo Giunchi ◽  
...  
Keyword(s):  
Tectonic Setting ◽  
Normal Fault ◽  
Historical Earthquakes ◽  
Northern Apennines ◽  
Tectonic Activity ◽  
Economic Losses ◽  
Depth Interval ◽  
Time Interval ◽  
Stress Regime ◽  
Ground Shaking

<p>The Northern Apennines is a NW-SE striking fold-and-thrust belt composed of a pile of NE-verging tectonic units that developed during Cenozoic collision between the European plate (Corso–Sardinian block) and the Adria plate. Seismicity and geodetic data indicate that contemporaneous crustal shortening (in the external, Adriatic part) and extension (in the internal, Tyrrhenian side) characterize the current tectonic activity of the Apennines. The region around the Mugello basin (Northern Tuscany) represents one of the most important seismogenic areas of the Northern Apennines. Large historical earthquakes have occurred, such as the M=6.0, 1542 and the M=6.4, 1919 events. Its proximity to densely-urbanized areas and the potential impact of strong earthquakes on the cultural heritage in the nearby (~30km) city of Florence makes a better knowledge of the seismicity in the Mugello basin a target of paramount importance. Unresolved issues regard (i) the exact location and geometry of the fault(s) which produced the 1542 and 1919 earthquakes, (ii) the mechanism driving the abrupt transition from an extensional to compressional stress regime at the internal and external sides of the belt, respectively, and (iii) geometry of and role played by a close-by transfer zone oriented transversely (NE-SW) to the main strike of the belt. To address these problems, in early 2019 we initiated a project aiming at improving the knowledge about the seismo-tectonic setting of the basin and adjoining areas. At first, we integrated all the available seismic catalogs for the area, obtaining more than 12000 earthquakes spanning the 2005-2019 time interval. These data have been used to derive a minimum-misfit, 1-D velocity model to be subsequently used for a travel times inversion 3D tomography. At the same time, we Installed 9 temporary seismic stations, complementing the permanent networks presently operating in the area. This new deployment recorded a Mw=4.5 earthquake that struck the NW margin of the basin on Dec. 9, 2019. The mainshock and the ~200 aftershocks precisely delineate a 5-km-long, NW-striking and SW-dipping fault which extends over the 6-9 km depth interval. The focal mechanism of the mainshock yields consistent results, indicating a normal fault striking N105°E and dipping about 45°. This fault appears to be distinct from that (those) activated during the two last important sequences in the area, which occurred in 2008 and 2009. The earthquake caused unexpected, large accelerations (PGA~0.24g at ~7km epicentral range), provoking damages that resulted in the evacuation of more than 150 residents and economic losses of several millions of euro. Sample horizontal-to-vertical spectral ratios at the most damaged sites report significant amplification within the 1-5 Hz frequency range, likely responsible for the anomalous ground shaking. Given the proximity of the aforementioned fault to that inferred for the 1542 (and, possibly, 1919) earthquake(s), a detailed study of the 2019 seismic sequence is expected to shed new light into the overall dynamics of the basin.</p>

Basement-controlled Neogene polyphase cover thrusting and basin development along the Chianti Mountains ridge (Northern Apennines, Italy)

1999 ◽  
Vol 136 (2) ◽  
pp. 133-152 ◽  
Author(s):  
MARCO BONINI
Keyword(s):  
Sedimentary Cover ◽  
Normal Fault ◽  
Northern Apennines ◽  
Fault System ◽  
Time Interval ◽  
Tectonic Structures ◽  
Quaternary Period ◽  
Deformation Stages ◽  
Thrust System ◽  
Continental Basin

The Chianti Mountains is an important sector of an E-verging regional thrust-related fold (the so-called Tuscan Nappe) extending along the whole length of the Northern Apennines. This thrust system involves the Tuscan Sequence superposing the Macigno sandstones onto Cervarola-Falterona sandstones, both of which are sedimented in adjacent foredeep basins. Detailed field mapping and analysis of superposition relations among tectonic structures, as well as correlation between structures and syntectonic deposition, has allowed Chianti Mountain evolution to be interpreted in terms of three main stages of deformation.The D1 stage resulted in the NE-directed synsedimentary thrusting of the Macigno onto the Cervarola-Falterona sandstones, while large NE to ENE-vergent thrust-related folds developed during the two successive deformation stages (D2 and D3). Fault-propagation folds developed during the D2 stage, and were affected by the Main Chianti Mountains Thrust (MCMT) during the successive D3 stage. In particular, the D3 stage has been correlated to the development, during the Pliocene period, of the hinterland Upper Valdarno Basin, which was previously considered to be an extensional basin. In fact, this continental basin formed along the eastern margin of the Chianti Mountains, ahead of the MCMT that also produced a shortening of the basin fill. With the beginning of the Quaternary period, the tectonic regime switched to extensional, as manifested by the development of a normal fault system on the opposite basin margin.The data presented here allow us to infer that the Chianti Mountains thrust system (D2 and D3) developed during a time interval spanning from the Late Miocene (∼12 Ma) until the Late Pliocene (∼2 Ma) periods. In the Northern Apennines, polyphase thrusting recorded by cover rocks has been related to the activity of basement thrusts, which have been recently evidenced by geophysical data. In this context, the two latest stages of deformation recognised in the Chianti Mountains have been attributed to the activity of the Abetone–Cetona crustal thrust, the deformational effects of which propagated forward in the sedimentary cover.

scholarly journals Deformation Pattern of the Northern Sector of the Malta Escarpment (Offshore SE Sicily, Italy): Fault Dimension, Slip Prediction, and Seismotectonic Implications

2021 ◽  
Vol 8 ◽  
Author(s):  
Salvatore Gambino ◽  
Giovanni Barreca ◽  
Felix Gross ◽  
Carmelo Monaco ◽  
Sebastian Krastel ◽  
...  
Keyword(s):  
Historical Earthquakes ◽  
Tectonic Activity ◽  
Recurrence Time ◽  
Time Interval ◽  
Deformation Pattern ◽  
Active Deformation ◽  
Seismic Reflection Data ◽  
Reflection Data ◽  
Bathymetric Grids ◽  
Northern Sector

Marine seismic reflection data coupled with on-land structural measurements improve our knowledge about the active deformation pattern of the northern sector of the Malta Escarpment, a bathymetric and structural discontinuity in the near-offshore of Eastern Sicily. As favourably oriented to be reactivated within the Neogene Africa–Europe convergence, it is believed that the Malta Escarpment has a significant role in the recent seismotectonic framework of the Western Ionian Basin and the Hyblean foreland domain of SE Sicily, where some of the largest and most destructive Mediterranean earthquakes are located according to available historical catalogs. Offshore seismic data along with bathymetric grids illuminate the shallow subseafloor setting and allow more accurate mapping of the seafloor expression of previously identified faults in the area. The seismic interpretation and the near-fault sediment pattern analysis provide constraints on fault 3D geometries as well as on their through-time tectonic activity, suggesting also that part of the observed deformation may have been caused by nontectonic processes. Identified faults form currently an E-dipping, roughly N–S trending, and 60 km-long extensional belt deforming the seafloor with a significant displacement amount in the Ionian offshore between Catania and Siracusa. 3-dimensional parameters of faults were then used to derive expected magnitudes and their reactivation propensity. Empirical scaling relationships and forward methods point to a high seismic potential for the detected fault as well as predict the fault slip behavior according to the field-derived differential stress. This combined analysis along with faults displacement measurements pointed out how the longest and most continuous fault could be capable of generating M > 7 seismic events, putting forward strong seismotectonic implications for the adjacent and densely populated Hyblean Plateau. The expected magnitude and the estimated recurrence time interval are compatible with those inferred for large historical earthquakes in the area even if other offshore seismic sources cannot be ruled out.

scholarly journals Past earthquake timing and magnitude along the Inglewood fault, Taranaki, New Zealand

1994 ◽  
Vol 27 (2) ◽  
pp. 155-162 ◽  
Author(s):  
A. G. Hull
Keyword(s):  
Volcanic Ash ◽  
Surface Displacement ◽  
Normal Fault ◽  
Historical Earthquakes ◽  
Normal Faults ◽  
Single Event ◽  
Ground Shaking ◽  
Large Earthquakes ◽  
Fault Length ◽  
Strong Ground

Several active normal faults in the onshore and offshore regions of Taranaki are capable of generating large earthquakes and associated strong ground shaking. Historical earthquakes are concentrated offshore of Cape Egmont, and no significant earthquakes have been detected along the major onshore surface faults. The northeaststriking Inglewood fault is a major onshore, southward-dipping normal fault. It has a known length of c. 20 km and an average scarp height of c. 3 m on landforms less than about 15,000 yrs old. Three subsurface excavations at two sites along the Inglewood fault about 15 km from New Plymouth have revealed three surface fault displacements during the last c. 13,000 years. Earthquakes resulting in about 1.2 m of surface displacement occurred at c. 3,500 radiocarbon yrs BP; between 4,000 and 9,000 radiocarbon yrs BP; and between 10,000 and 13,000 radiocarbon yrs BP, judged by the amount of vertical offset of dated volcanic ash layers. Based on average single-event fault slip values of 1.2-3.0 m and a fault length of 20-30 km, the estimated earthquake magnitudes associated with these past movements range from Mw 6.7 to 7.2.

scholarly journals THE STREAM-LENGTH GRADIENT INDEX AND THE CORRESPONDING LANDFORM STRUCTURES OVER THE KIULU RIVER, NORTHWEST SABAH

2020 ◽  
Vol 4 (1) ◽  
pp. 26-28
Author(s):  
Chung Wei Kiat ◽  
Felix Tongkul
Keyword(s):  
Normal Fault ◽  
Historical Earthquakes ◽  
Tectonic Activity ◽  
Gradient Index ◽  
Stream Length ◽  
Sudden Drop ◽  
River Diversions ◽  
The Relationship

In this paper, we explored the relationship between the stream-length gradient index over the Kiulu River upstream and its respective landform. The knickpoints derived from stream-length gradient index detected sudden drop in elevation that may be associated with recent tectonic activity over NW Sabah. To illustrate the changes in the stream profile, two knickpoints, F1 which coincided with historical earthquakes, and F2 which showed peak anomaly are selected. The landform over knickpoint F1 showed river diversions whereas the landform over knickpoint F2 showed deep ponding. Both field sites, however showed consistent alternation between rapids and ponding forming a step-like landform where the inferred normal fault is oriented at N40E. The stretched landform over the Kiulu river sites supports an extension setting that may be associated with gravity-sliding tectonics over NW Sabah.

scholarly journals A Normal Faults System in the Monte Nerone area and its significance in the recent seismo-tectonic setting of the Northern Umbria-Marche Apennines (Italy)

2021 ◽  
Author(s):  
Mauro De Donatis ◽  
Giulio Fabrizio Pappafico ◽  
Sara Susini ◽  
Mauro Alberti ◽  
Nelson Muñoz Guerrero ◽  
...  
Keyword(s):  
Tectonic Setting ◽  
Historical Earthquakes ◽  
Tectonic Activity ◽  
Normal Faults ◽  
Seismic Events ◽  
Field Mapping ◽  
Marche Region ◽  
Extensional Tectonic ◽  
Original Field ◽  
Recent Activity

Abstract. The faults system mapped in the northern Marche Apennines, the NW sector of Monte Nerone, Italy, shows many indications of recent activity. This area has been affected by some strong historical earthquakes, such as the Cagli earthquake of 1781, similar to seismic events close by affecting the southern Marche, Umbria, Lazio, and Abruzzi areas in recent years, we focused our investigation on this sector. The original field mapping work integrated with seismic and subsurface data suggests very similar genesis and kinematics to those of the recent seismic events in the south of Marche region. In addition, this interpretation could also attest the extensional tectonic activity affecting the whole Adriatic side of the watershed backbone of this sector of the Apennines, with probable inversion of involved previous compressional features, such as thrust ramps.

Hematite (U-Th)/He constraints on Plio-Pleistocene deformation and hydrothermalism in the eastern Island of Elba, northern Apennines (Italy)

2020 ◽  
Author(s):  
Giulio Viola ◽  
Alexis Derycke ◽  
Cécile Gautheron ◽  
Francesco Mazzarini ◽  
Giovanni Musumeci ◽  
...  
Keyword(s):  
Late Miocene ◽  
Structural Model ◽  
Slip Surface ◽  
Normal Fault ◽  
Fault Gouge ◽  
Northern Apennines ◽  
Time Interval ◽  
Mining District ◽  
Tyrrhenian Sea ◽  
Constrained Deformation

<p>The northern Tyrrhenian Sea and the inner northern Apennines (NA) are classically regarded as a late Miocene–Pleistocene back-arc system characterized by crustal extension and acidic magmatism coeval with shortening farther east at the front of the belt. The orogenic prism of the NA, which is well exposed in the easternmost Island of Elba, formed by eastward thrusting, stacking and folding of oceanic and continental units from the Eocene down to the late Miocene. Eastern Elba hosts the historically and economically most important Fe district of Italy, which, in the study area, consists of sulphide- and Fe-rich veins and breccias, in addition to minor massive Fe ore bodies of hydrothermal origin emplaced in actively deforming upper crustal conditions (Mazzarini et al., JSG, 2019). The Zuccale fault (ZF) on Elba is generally interpreted as a major normal fault, which would have greatly facilitated regional E-W extension during the late Miocene. It is an east-dipping low angle fault that displaces the nappe pile by up to 6 km. The fault architecture is complex, although it can be approximated by an exclusively brittle, flat-lying component dated to < c. 5 Ma by K-Ar on illite from fault gouge that cuts through steeper, brittle-ductile and earlier top-to-the E thrust related fabrics (Viola et al., Tectonics, 2018).</p><p>Aiming at directly constraining the syn- to post Pliocene evolution of the ZF and the age of the hydrothermal Fe deposits of the historic mining district, we performed hematite (U-Th)/He dating of the low-angle, hematite-decorated principal slip surface of the ZF at the famous Terra Nera section. Hematite samples examined in this study comprise platelet-shaped crystals (specularite), fine aggregates coating fault slip surfaces, massive veins, the fine matrix of breccias, and euhedral millimetric crystals from low strain domains. Ages from the ZF striated fault plane span the ~4.2±0.4 to 3.6±0.4 Ma time interval, fully consistent with available fault gouge illite K-Ar dates. Later NNE-SSW strike-slip faulting, associated with centimetric specularite veins, is constrained to between 2.1±0.2 and 1.7±0.2 Ma, roughly coeval with transient and local reactivation of the ZF as indicated by 1.9±0.2-1.5±0.2 Ma old euhedral, millimetric hematite infilling dilational jogs within the foliated ZF fault zone. Farther north, in the Rio Albano area, mineralised hematite breccias genetically associated with top-to-the E spectacular extensional faults are dated to between 1.6±0.2 and 0.9±0.1 Ma and postdate older ~2.7-2.6 Ma quartz-hematite veins associated with a discrete phase of top-to-the W shearing.</p><p>All obtained dates fit our independently built structural model of the investigated area, where clear crosscutting relationships and structural/metamorphic considerations have permitted establishing a sequence of kinematically constrained deformation events. For the first time we have defined the exact timing of deformation in the study area, contributing to the unravelling of the local, long and complex tectonic and mineralization history and to a better constrained regional picture.</p>

scholarly journals Tectono-Sedimentary Evolution of the Cenozoic Basins in the Eastern External Betic Zone (SE Spain)

Geosciences ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 394
Author(s):  
Manuel Martín-Martín ◽  
Francesco Guerrera ◽  
Mario Tramontana
Keyword(s):  
Strike Slip ◽  
Alluvial Fan ◽  
Tectonic Activity ◽  
Time Interval ◽  
Se Spain ◽  
The Third ◽  
Sedimentary Evolution ◽  
Marine Sedimentation ◽  
Geodynamic Processes ◽  
Early Paleocene

Four main unconformities (1–4) were recognized in the sedimentary record of the Cenozoic basins of the eastern External Betic Zone (SE, Spain). They are located at different stratigraphic levels, as follows: (1) Cretaceous-Paleogene boundary, even if this unconformity was also recorded at the early Paleocene (Murcia sector) and early Eocene (Alicante sector), (2) Eocene-Oligocene boundary, quite synchronous, in the whole considered area, (3) early Burdigalian, quite synchronous (recognized in the Murcia sector) and (4) Middle Tortonian (recognized in Murcia and Alicante sectors). These unconformities correspond to stratigraphic gaps of different temporal extensions and with different controls (tectonic or eustatic), which allowed recognizing minor sedimentary cycles in the Paleocene–Miocene time span. The Cenozoic marine sedimentation started over the oldest unconformity (i.e., the principal one), above the Mesozoic marine deposits. Paleocene-Eocene sedimentation shows numerous tectofacies (such as: turbidites, slumps, olistostromes, mega-olistostromes and pillow-beds) interpreted as related to an early, blind and deep-seated tectonic activity, acting in the more internal subdomains of the External Betic Zone as a result of the geodynamic processes related to the evolution of the westernmost branch of the Tethys. The second unconformity resulted from an Oligocene to Aquitanian sedimentary evolution in the Murcia Sector from marine realms to continental environments. This last time interval is characterized as the previous one by a gentle tectonic activity. On the other hand, the Miocene sedimentation was totally controlled by the development of superficial thrusts and/or strike-slip faults zones, both related to the regional geodynamic evolutionary framework linked to the Mediterranean opening. These strike-slip faults zones created subsidence areas (pull-apart basin-type) and affected the sedimentation lying above the third unconformity. By contrast, the subsidence areas were bounded by structural highs affected by thrusts and folds. After the third unconformity, the Burdigalian-Serravallian sedimentation occurred mainly in shallow- to deep-water marine environments (Tap Fm). During the Late Miocene, after the fourth unconformity, the activation of the strike-slip faults zones caused a shallow marine environment sedimentation in the Murcia sector and a continental (lacustrine and fluvial) deposition in the Alicante sector represented the latter, resulting in alluvial fan deposits. Furthermore, the location of these fans changed over time according to the activation of faults responsible for the tectonic rising of Triassic salt deposits, which fed the fan themselves.

scholarly journals The Role of Seismological Networks in Civil Protection in Low and High Seismic Hazards

2021 ◽  
Author(s):  
Erzsébet Győri ◽  
Arman Bulatovich Kussainov ◽  
Gyöngyvér Szanyi ◽  
Zoltán Gráczer ◽  
Kendebay Zhanabilovich Raimbekov ◽  
...  
Keyword(s):  
Early Warning ◽  
Early Warning Systems ◽  
Economic Losses ◽  
Civil Protection ◽  
Warning Systems ◽  
Ground Shaking ◽  
Research Areas ◽  
Seismic Networks ◽  
Strong Ground

Earthquakes are one of the most devastating natural disasters on Earth, causing sometimes huge economic losses and many human casualties. Since earthquake prediction is not yet possible, the purpose of civil protection is to reduce damage and protect human lives, in which the seismological networks of different countries play a very important role. Special applications of seismic networks are the early warning systems that can be used to protect vulnerable infrastructures using automated shutdown procedures, to stop high velocity trains and to save lives if the general public is notified about imminent strong ground shaking. In this paper, we describe the aims and operation of seismological networks, covering in more detail the early warning systems. Then we delineate the seismotectonic settings and seismicity in Hungary and Kazakhstan, furthermore, describe the operating seismological networks and the related scientific research areas with emphasis on civil protection. Hungary and Kazakhstan differ not only in the size of their territory, but also in their seismicity, therefore, in addition to the similarities, there are also significant differences between the aims and problems of their seismological networks.

scholarly journals Neogene-Quaternary tectonic regime and macroseismic observations in the Tyrnavos-Elassona broader epicentral area of the March 2021, intense earthquake sequence

2021 ◽  
Vol 58 ◽  
pp. 200
Author(s):  
Dimitrios Galanakis ◽  
Sotiris Sboras ◽  
Garyfalia Konstantopoulou ◽  
Markos Xenakis
Keyword(s):  
Normal Fault ◽  
Fault Scarp ◽  
Focal Mechanisms ◽  
Fault System ◽  
Spatiotemporal Evolution ◽  
Surface Rupture ◽  
Alluvial Deposits ◽  
Epicentral Area ◽  
Ground Shaking ◽  
Macroseismic Observations

On March 3, 2021, a strong (Mw6.3) earthquake occurred near the towns of Tyrnavos and Elassona. One day later (March 4), a second strong (Mw6.0) earthquake occurred just a few kilometres toward the WNW. The aftershock spatial distribution and the focal mechanisms revealed NW-SE-striking normal faulting. The focal mechanisms also revealed a NE-SW oriented extensional stress field, different from the orientation we knew so far (ca. N-S). The magnitude and location of the two strongest shocks, and the spatiotemporal evolution of the sequence, strongly suggest that two adjacent fault segments were ruptured respectively. The sequence was followed by several coseismic ground deformational phenomena, such as landslides/rockfalls, liquefaction and ruptures. The landslides and rockfalls were mostly associated with the ground shaking. The ruptures were observed west of the Titarissios River, near to the Quaternary faults found by bore-hole lignite investigation. In the same direction, a fault scarp separating the alpidic basement from the alluvial deposits of the Titarissios valley implies the occurrence of a well-developed fault system. Some of the ground ruptures were accompanied by extensive liquefaction phenomena. Others cross-cut reinforced concrete irrigation channels without changing their direction. We suggest that this fault system was partially reactivated, as a secondary surface rupture, during the sequence as a steeper splay of a deeper low-to-moderate angle normal fault.

scholarly journals The 31 March 2020 Mw 6.5 Stanley, Idaho, Earthquake: Seismotectonics and Preliminary Aftershock Analysis

2020 ◽  
Author(s):  
Lee M. Liberty ◽  
Zachery M. Lifton ◽  
T. Dylan Mikesell
Keyword(s):  
Surface Displacement ◽  
Volcanic Belt ◽  
Normal Fault ◽  
Fault System ◽  
Basin And Range Province ◽  
Ground Shaking ◽  
The North ◽  
Show Evidence ◽  
Tectonic Framework ◽  
Tectonic Belt

Abstract We report on the tectonic framework, seismicity, and aftershock monitoring efforts related to the 31 March 2020 Mw 6.5 Stanley, Idaho, earthquake. The earthquake sequence has produced both strike-slip and dip-slip motion, with minimal surface displacement or damage. The earthquake occurred at the northern limits of the Sawtooth normal fault. This fault separates the Centennial tectonic belt, a zone of active seismicity within the Basin and Range Province, from the Idaho batholith to the west and Challis volcanic belt to the north and east. We show evidence for a potential kinematic link between the northeast-dipping Sawtooth fault and the southwest-dipping Lost River fault. These opposing faults have recorded four of the five M≥6 Idaho earthquakes from the past 76 yr, including 1983 Mw 6.9 Borah Peak and the 1944 M 6.1 and 1945 M 6.0 Seafoam earthquakes. Geological and geophysical data point to possible fault boundary segments driven by pre-existing geologic structures. We suggest that the limits of both the Sawtooth and Lost River faults extend north beyond their mapped extent, are influenced by the relic trans-Challis fault system, and that seismicity within this region will likely continue for the coming years. Ongoing seismic monitoring efforts will lead to an improved understanding of ground shaking potential and active fault characteristics.

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