scholarly journals Seismic Soil Characterization to Estimate Site Effects Induced by Near-Fault Earthquakes: The Case Study of Pizzoli (Central Italy) during the Mw 6.7 2 February 1703, Earthquake

Geosciences ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 2
Author(s):  
Anna Chiaradonna ◽  
Marco Spadi ◽  
Paola Monaco ◽  
Felicia Papasodaro ◽  
Marco Tallini
Keyword(s):  
Site Effects ◽  
Water Pressure ◽  
Central Italy ◽  
Active Faults ◽  
Soil Liquefaction ◽  
Ground Failure ◽  
Near Fault ◽  
Local Seismic Response ◽  
Seismic Site Effects ◽  
Near Fault Earthquakes

Many of the urban settlements in Central Italy are placed nearby active faults and, consequently, the ground motion evaluation and seismic site effects under near-fault earthquakes are noteworthy issues to be investigated. This paper presents the results of site investigations, the seismic site characterization, and the local seismic response for assessing the effects induced by the Mw 6.7 2 February 1703, near-fault earthquake at the Madonna delle Fornaci site (Pizzoli, Central Italy) in which notable ground failure phenomena were observed, as witnessed by several coeval sources. Even though recent papers described these phenomena, the geological characteristics of the site and the failure mechanism have never been assessed through in-situ investigations and numerical modeling. Within a project concerning the assessment of soil liquefaction potential and co-seismic ground failure, deep and shallow continuous core drilling, geophysical investigations and in-hole tests have been carried out. Subsequently, the geotechnical model has been defined and the numerical quantification of the different hypotheses of failure mechanisms has been evaluated. Analyses showed that liquefaction did not occur, and the excess pore water pressure induced by the shaking was not the source of the ground failure. Therefore, it was hypothesized that the sinkhole was likely caused by earthquake-induced gas eruption.

Seismic characterization of Pizzoli (Central Italy) to estimate site effects induced by near-fault earthquakes

2021 ◽  
Author(s):  
Marco Tallini ◽  
Paola Monaco ◽  
Marco Spadi ◽  
Anna Chiaradonna ◽  
Felicia Papasodaro
Keyword(s):  
Ground Motion ◽  
Active Fault ◽  
Central Italy ◽  
Soil Liquefaction ◽  
Core Drilling ◽  
Near Fault ◽  
Near Fault Earthquakes ◽  
Subsoil Model ◽  
Near Fault Ground Motion

<p>Most of the towns, villages and infrastructures settled in Central Italy are placed nearby active faults and, consequently, the ground motion evaluation and the ground failures characterization under near-fault earthquakes are noteworthy issues to be investigated. The Madonna delle Fornaci - MDF – site, close to Pizzoli village (L’Aquila in Central Italy), has been selected as an emblematic site for assessing the effects induced by near-fault earthquakes, because it is located very close to the Pizzoli-Barete active Fault accountable for the February 2, 1703 Mw 6.67 earthquake. After this historical earthquake, remarkable surface manifestations, attributed to soil liquefaction and coseismic ground sinkholes, were observed at the MDF site, occurred in the Holocene alluvial deposit of the Aterno River, as witnessed by several written sources (among which Uria De Llanos, 1703). As concerns the geological setting, the MDF site is placed in the Plio-Quaternary NW-SE elongated L’Aquila intramontane basins which is bounded by a framework of active NW-SE trending and SW-dipping extensional faults which includes also the above mentioned Pizzoli-Barete active Fault. A comprehensive geophysical, geological, and geotechnical campaign has been carried out at the MDF site with the goal to obtain the seismic site characterization and the shallow and deep subsoil model preparatory to the quantitative estimation of the near-fault ground motion and the evaluation of the soil liquefaction potential induced by the 1703 seismic event.</p><p>The field survey consisted of three shallow continuous core drilling 15-20 m-deep boreholes; in one of the them, a down hole test and SPT measurements were conducted every 1 m depth; an open tube piezometer at the 11-12 m depth was installed in one of the boreholes; a couple of undisturbed samples were sampled for geotechnical laboratory tests; a MASW, Seismic refraction and ERT investigations were performed along two perpendicular 70-m long alignments; several single station microtremor measurements performed also in the neighbouring area. These data permitted preliminary to elaborate a quite confident 1-2D litho- and seismo-stratigraphic model for the MDF test site.</p><p>The MDF site is characterized by mainly calcareous grain-supported Holocene alluvial deposit: sandy gravel and gravelly sand with a silty component, sometimes predominant, in the matrix with water table level about 8-12 m b.g.l. Moreover, the following horizons are noteworthy to mention: an orange sand level at 11-12 m b.g.l. which could be considered preliminary as a liquefaction-prone level and an organic reddish-brown silty clay at 14-15 m b.g.l., which could be used for C14 dating.</p><p>Further, a 200 m-deep continuous core drilling borehole, executed nearby the MDF site by ISPRA for the mapping of the Italian geological sheet 348 “Antrodoco”, was also taken into consideration to obtain the complete 1D subsoil model for the near-fault ground motion amplification modelling.</p><p>The near-fault ground motion evaluation of the MDF site, considered as paradigmatic of the Central Italy seismicity, will go on through the geotechnical characterization of the alluvial deposits, the shear wave velocity versus depth profile and the seismic input evaluation to use for the numerical modelling.</p>

Earthquake Proof Efficiency of Sliding Base Isolator With Dog-Bone Type Damping

2005 ◽  
Author(s):  
C. S. Tsai ◽  
Tsu-Cheng Chiang ◽  
Bo-Jen Chen
Keyword(s):  
Ground Motions ◽  
Active Faults ◽  
Friction Behavior ◽  
Near Fault ◽  
The Past ◽  
Numerical Studies ◽  
Dog Bone ◽  
Base Isolator ◽  
Near Fault Earthquakes ◽  
Base Isolators

In recent years, there have been more and more seismic retrofit applications of using base isolators in seismic prone regions. In the past, the focuses of researches on the efficiency of various base isolators have been aimed at their behavior under earthquakes without long predominant periods. The doubts of efficiency of the base isolator nearby active faults or located at a soft deposit soil have been raised by researchers. It is revealed from previous studies that the seismic responses of the base isolated structure are significant due to the influence of resonance. In order to minimize the inherent shortcomings of base isolators, various base isolators with dog bone type of friction behavior have been proposed in this study. In the meanwhile, the exact solutions used to describe the behavior of the proposed isolators have also been derived in this study. The numerical studies show that the displacement responses of proposed isolators under near fault earthquakes and ground motions with long predominant periods are much lower than those of the traditional FPS and VCFPS devices. Hence, the required dimensions of proposed isolators can be smaller than those for the FPS and VCFPS isolators.

Extending near fault earthquakes catalogs using convolutional neural network and single-station waveforms

2020 ◽  
Author(s):  
Josipa Majstorović ◽  
Piero Poli
Keyword(s):  
Central Italy ◽  
Warning System ◽  
Night Time ◽  
Earthquake Early Warning System ◽  
Near Fault ◽  
Earthquake Detection ◽  
Single Station ◽  
Seismic Catalogs ◽  
Near Fault Earthquakes ◽  
The City

<p>The machine learning (ML) algorithms have already found their application in standard seismological procedures, such as earthquake detection and localization, phase picking, earthquake early warning system, etc. They are progressively becoming superior methods since one can rapidly scan voluminous data and detect earthquakes, even if buried in highly noisy time series.</p><p>We here make use of ML algorithms to obtain more complete near fault seismic catalogs and thus better understand the long-term (decades) evolution of seismicity before large earthquakes occurrence. We focus on data recorded before the devastating L’Aquila earthquake (6 April 2009 01:32 UTC, Mw6.3) right beneath the city of L’Aquila in the Abruzzo region (Central Italy). Before this event sparse stations were available, reducing the magnitude completeness of standard catalogs. </p><p>We adapted existing convolutional neural networks (CNN) for earthquake detection, localisation and characterization using a single-station waveforms. The CNN is applied to 29 years of data (1990 to 2019) recorded at the AQU station, located near the city of L’Aquila (Italy). The pre-existing catalog maintained by Istituto nazionale di geofisica e vulcanologia is used to define labels and train and test the CNN. We are here interested in classifying the continuous three-component waveforms into four categories, noise/earthquakes, distance (location), magnitude and depth, where each category consists of several nodes. Existing seismic catalogs are used to label earthquakes, while the noise events are randomly selected between the catalog events, evenly represented by daytime and night-time periods.</p><p>We prefer CNN over other methods, since we can use seismograms directly with very minor pre-processing (e.g. filtering) and we do not need any prior knowledge of the region.</p><p><br><br></p>

Local Seismic site effects estimated by detailed seismic surveys: the case of Castelnuovo village (L’Aquila Basin, central Italy)

2021 ◽  
Author(s):  
Marco Spadi ◽  
Marco Tallini ◽  
Matteo Albano ◽  
Domenico Cosentino ◽  
Marco Nocentini ◽  
...  
Keyword(s):  
Cross Sections ◽  
Site Effects ◽  
Dynamic Properties ◽  
Central Italy ◽  
Earthquake Hazard ◽  
Small Scale ◽  
Seismic Site Effects ◽  
New Findings ◽  
Subsoil Model ◽  
Observed Damage

<p>Assessing seismic site effects is essential in earthquake hazard studies. Local seismic amplification is strongly related to the site stratigraphy and topography, the dynamic properties of the subsoil deposits, and the earthquake features. The evaluation of these factors is mandatory to achieve a consistent model of the seismic hazard at small scale. Here we discuss the case of Castelnuovo village (L’Aquila, central Italy). Located on a small ridge, approximately 60 m higher than the valley floor, the village was heavily struck by April 6, 2009, M<sub>w</sub> 6.3 L’Aquila earthquake, with catastrophic collapse of several buildings. Previous studies ascribed the observed damage to the presence of shallow caves beneath the buildings or to the topographic amplification.</p><p>In this work, an updated and detailed subsoil model for Castelnuovo site has been provided, based updated geological surveys, such as borehole logs and geophysical data consisting in microtremor measurements and down-hole.</p><p>These measurements identified resonant frequencies occurring in the range of 0.7-3.0 Hz. These frequency peaks are related to the presence of a velocity contrast at depth between the San Nicandro silts and the Madonna della Neve breccias, as indicated by the performed deep boreholes. Thanks to analytical, numerical, and geostatistical techniques, we identified the main impedance contrast at approximately 210 m depth from the top of the hill, much deeper than previous studies. These new findings allowed to create an accurate and consistent subsoil model summarized by two geological cross-sections of the Castelnuovo ridge, showing that the seismic site effects at the Castelnuovo village are mainly related to stratigraphic amplification.</p>

scholarly journals The Effect of Ground Motion Selection Methods for Seismic Design of Tall Buildings: A Case Study of Mandalay City

2020 ◽  
Vol 17 (12) ◽  
pp. 1348-1355
Author(s):  
Yan Naung KO ◽  
Teraphan ORNTHAMMARATH
Keyword(s):  
Ground Motion ◽  
Response Spectrum ◽  
Active Faults ◽  
Structural Response ◽  
Tall Buildings ◽  
Lateral Force ◽  
Far Field ◽  
Ground Motion Selection ◽  
Near Fault ◽  
Near Fault Earthquakes

The near-fault earthquakes ground motion usually observed a few kilometers away from the active faults generally contains high energetic velocity pulses as a consequence of directivity effects. Mandalay city is located 8 km away from the Sagaing fault, and the comparative study is conducted to evaluate the structural response of 3 different types of Reinforced Concrete buildings - 4-story, 10-story, and 16-story buildings, respectively. These buildings are subjected to bi-directional ground motions selected from both far-field and pulse-like near-fault earthquakes. The far-field earthquakes produce less seismic demand on the buildings when compared to the near-fault earthquakes, where the ratio of the fundamental period of the building to the pulse period is significant. Comparing 2 ground motion selection and scaling methods of Tall Building Initiative guidelines - TBI (2010) and TBI (2017), the latter approach provides a more meaningful definition of intensity measure and allows reducing some conservatism. The structural response obtained from the design Equivalent Lateral Force (ELF) and Response Spectrum Analysis (RSA) is compared with the code-based linear Response History Analysis (RHA) results.

Design ground motions near active faults

2009 ◽  
Vol 42 (1) ◽  
pp. 1-8 ◽  
Author(s):  
Jonathan D. Bray ◽  
Adrian Rodriguez-Marek ◽  
Joanne L. Gillie
Keyword(s):  
Urban Areas ◽  
Site Effects ◽  
Site Response ◽  
Ground Motions ◽  
Soft Soil ◽  
Active Faults ◽  
Peak Ground Velocity ◽  
Near Fault ◽  
Effective Performance ◽  
Lower Magnitude

Forward-Directivity (FD) in the near-fault region can produce intense, pulse-type motions that differ significantly from ordinary ground motions that occur further from the ruptured fault. Near-fault FD motions typically govern the design of structures built close to active faults so the selection of design ground motions is critical for achieving effective performance without costly over-design. Updated empirical relationships are provided for estimating the peak ground velocity (PGV) and period of the velocity pulse (Tv) of near-fault FD motions. PGV varies significantly with magnitude, distance, and site effects. Tv is a function of magnitude and site conditions with most of the energy being concentrated within a narrow-period band centred on the pulse period. Lower magnitude events, which produce lower pulse periods, might produce more damaging ground motions for the stiff structures more common in urban areas. As the number of near-fault recordings is still limited, fully nonlinear bi-directional shaking simulations are employed to gain additional insight. It is shown that site effects generally cause Tv to increase. Although the amplification of PGV at soil sites depends on site properties, amplification is generally observed even for very intense rock motions. At soft soil sites, seismic site response can be limited by the yield strength of the soil, but then seismic instability may be a concern.

scholarly journals Influence of Elastomeric Bearings in Tension on the Seismic Performance of Base-Isolated r.c. Buildings

2020 ◽  
Vol 11 (1) ◽  
pp. 82
Author(s):  
Fabio Mazza ◽  
Mirko Mazza
Keyword(s):  
Base Isolation ◽  
Nonlinear Models ◽  
Vertical Component ◽  
Computer Code ◽  
Nonlinear Phenomena ◽  
Isolation System ◽  
Elastomeric Bearings ◽  
Near Fault ◽  
Base Isolation System ◽  
Near Fault Earthquakes

Elastomeric bearings are commonly used in base-isolation systems to protect the structures from earthquake damages. Their design is usually developed by using nonlinear models where only the effects of shear and compressive loads are considered, but uncertainties still remain about consequences of the tensile loads produced by severe earthquakes like the near-fault ones. The present work aims to highlight the relapses of tension on the response of bearings and superstructure. To this end, three-, seven- and ten-storey r.c. framed buildings are designed in line with the current Italian seismic code, with a base-isolation system constituted of High-Damping-Rubber Bearings (HDRBs) designed for three values of the ratio between the vertical and horizontal stiffnesses. Experimental and analytical results available in literature are used to propose a unified nonlinear model of the HDRBs, including cavitation and post-cavitation of the elastomer. Nonlinear incremental dynamic analyses of the test structures are carried out using a homemade computer code, where other models of HDRBs considering only some nonlinear phenomena are implemented. Near-fault earthquakes with comparable horizontal and vertical components, prevailing horizontal component and prevailing vertical component are considered as seismic input. Numerical results highlight that a precautionary estimation of response parameters of the HDRBs is attained referring to the proposed model, while its effects on the nonlinear response of the superstructure are less conservative.

scholarly journals Seismic Response of RC Frames with a Soft First Story Retrofitted with Hysteretic Dampers under Near-Fault Earthquakes

2021 ◽  
Vol 11 (3) ◽  
pp. 1290
Author(s):  
Santiago Mota-Páez ◽  
David Escolano-Margarit ◽  
Amadeo Benavent-Climent
Keyword(s):  
Cost Effective ◽  
Far Field ◽  
Soft Story ◽  
Near Fault ◽  
Rc Frames ◽  
Story Drift ◽  
Number Of Cycles ◽  
Rc Frame Structures ◽  
Near Fault Earthquakes ◽  
Hysteretic Dampers

Reinforced concrete (RC) frame structures with open first stories and masonry infill walls at the upper stories are very common in seismic areas. Under strong earthquakes, most of the energy dissipation demand imposed by the earthquake concentrates in the first story, and this eventually leads the building to collapse. A very efficient and cost-effective solution for the seismic upgrading of this type of structure consists of installing hysteretic dampers in the first story. This paper investigates the response of RC soft-story frames retrofitted with hysteretic dampers subjected to near-fault ground motions in terms of maximum displacements and lateral seismic forces and compares them with those obtained by far-field earthquakes. It is found that for similar levels of total seismic input energy, the maximum displacements in the first story caused by near-fault earthquakes are about 1.3 times larger than those under far-field earthquakes, while the maximum inter-story drift in the upper stories and the distribution and values of the lateral forces are scarcely affected. It is concluded that the maximum displacements can be easily predicted from the energy balance of the structure by using appropriate values for the parameter that reflects the influence of the impulsivity of the ground motion: the so-called equivalent number of cycles.

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