Results of fundamental and applied seismological research in the Magadan region in 2016-2020

The results of fundamental and applied research, carried out by Magadan Branch of GS RAS during 2016-2020 in Magadan and Chukotka regions are presenting. Estimation of Seismic hazard of Russia’s Northeast (Magadan region) and seismic hazard maps for recurrence periods of 500, 1000 and 5000 years in scale close to that of detailed seismic zoning (DSZ) were made in cooperation with Institute of the Earth’s Physics RAS. In course of this work the estimation of initial seismic intensity and parameters of possible ground shaking in areas of critical facilities of Magadan region were made. For all of them a seismic micro zonation was carried out with methods of direct earthquake registration and comparing acoustic impedance. As result, a seismic amplification and intensity of seismic impact on the soils under main critical facilities were obtaining. The research results are shown on detailed seismic zoning maps that are basic for building projects of objects above.

Seismic microzonation of a region with complex surficial geology based on different site classification approaches

A seismic microzonation study was conducted to refine the seismic hazard model for the city of Saguenay, Canada. The Quaternary geology underlying Saguenay shows complex glacial and post-glacial stratigraphy with a number of buried valleys filled with fluvioglacial and glaciomarine sediments. High impedance contrast between rock formations and surficial sediments is prone to seismic amplification. To evaluate their applicability, advantages and limitations in capturing the geological specificity of the study area, four site classification methods were applied: the current National Building Code of Canada (NBCC) and Eurocode 8, both mainly based on the average shear-wave velocity for the surficial sediments (VS,avg) and for the top 30 m (VS,30); a method based on the fundamental site period (T0); and a hybrid method based on the combination of VS,30, T0 and VS,avg. The study specifically aimed to evaluate the importance of the site classification parameters on the resulting microzonation maps. VS,30 is capable to present the geological and geotechnical site conditions, however, the results may be further improved by considering Vs,avg in shallow and T0 in thick layers of soil sediments as secondary parameters. The T0 method gives also satisfactory results with T0 showing a better correlation to Vs,30 than to Vs,avg. The versatile hybrid method may be challenging to apply in certain cases with its nine different site categories and parameters.

Seismic Site Response of A Large Deep-seated Rock Slope Revealed by Field Monitoring and Geophysical Methods

Shidaguan Slope (hereinafter short for SDG Slope) is an unstable rock slope with an area of 30.78×104 m2 and a deformation depth of 30-70 m in Maoxian County, Sichuan Province, China. Three seismometers (P2-P4) with high sensitivity were installed at different locations on the unstable part of the slope. P2 and P3 were almost at the same elevation (2221 m and 2247 m), while P4 was the lowest (at 2140 m). Another seismometer (P1) sat in a stable location at a higher elevation (2373 m). 99 shallow earthquakes were analyzed. According to the peak acceleration ratios of three seismometers (P2-P4) on the unstable part and another seismometer (P1) on the stable part, the points at lower elevations showed greater seismic amplification (with the amplification coefficient of 2.64-3.51) than one at a higher elevation. And points at relatively thinner part (23 m thick) of unstable slope showed greater seismic amplification than ones at thick part (60-75 m thick). The same rule was also found in studying the site-epicenter azimuth and earthquake magnitude data. Based on the relationship between amplification coefficient and resistivity and rock core, the seismic response amplification was affected by the lithofacies difference. The lithofacies with resistivity values of 50-100 Ohm.m and RQD values of 0-50 % incurred seismic response amplification, which was restrained by the below lithofacies with resistivity values of 10-50 Ohm.m and ROD values of 0 %. When building on slope areas, the lithofacies difference should be taken into full consideration.

MzS Tools: GIS Methods and Tools for Seismic Microzonation Mapping

MzSTools is a plugin for QGIS developed by the National Research Council (CNR) as part of the activities concerning the coordination of seismic microzonation studies in Italy. It train from the need to create a practical and easy-to-use tool to carry out seismic microzonation (SM) studies by producing standards compliant geographic database and maps, thus making them accurate, homogeneous and uniform for all municipalities in Italy. A geodatabase based on SQLite/SpatiaLite Relational Database Management System (RDBMS). It has been designed to collect and store data related to elements such as: geognostic surveys; bedrocks and cover terrains; superficial and buried geomorphological elements; tectonic-structural elements; elements of geological instability such as landslide zones, liquefaction zones and zones affected by active and capable faults; homogeneous microzones in seismic perspective, microzones characterized by a seismic amplification factor. The QGIS plugin provides tools such as data entry forms designed with Qt Designer; a QGIS project template with layers, symbol libraries and graphic styles; layouts for the SM Maps. MzSTools assembles in a single software environment a set of useful tools for those who work in. The plugin is open source, whose code hosted on the GitHub platform, and is published via the official QGIS plugins repository (https://plugins.qgis.org/plugins/MzSTools/).

New Insights into Long-Period (>1 s) Seismic Amplification Effects in Deep Sedimentary Basins: A Case of the Po Plain Basin of Northern Italy

ABSTRACT This study investigates and quantifies the influence of the shallower deposits (down to few hundreds of meters) of the Po Plain sedimentary basin (northern Italy) on the long-period component (i.e., 1 s<T<3 s) of seismic ground motion, in which amplification effects due to the soft sediments above seismic bedrock were observed. A new seismostratigraphic model of the shallow deposits of the entire basin is provided with an unprecedented detail by taking advantage of recently acquired geophysical data. The seismostratigraphic model is used to simulate the ground motion amplification in the Po Plain by means of extensive 1D ground response analysis. Results are compared with seismic observations available at a number of sites equipped with borehole seismic stations, where earthquakes have been recorded both at the surface and at the seismic bedrock depth. Despite the general agreement with observations concerning the seismic resonance frequencies, our model may fail in capturing the amplitude of the actual seismic amplification of the basin in the long-period range. We observe that 3D basin effects related to surface waves generated at the edge of the basin may play a significant role in those zones where seismic hazard is controlled by distant sources. In these cases, 1D modeling leads to average underestimations of 30%, up to a maximum of 60%. The amplification functions need to be corrected for a basin-effects correction term, which in this case is provided by the ground-motion prediction equation of the study area. The corrected amplification functions agree with the empirical observations, overcoming the uneven distribution of the recording stations in strong-motion datasets. These results should be taken into account in future seismic microzonation studies in the Po Plain area, where the 1D approach is commonly adopted in ground response analyses, and in site-specific seismic hazard assessments aimed at the design of structures that are sensitive to the long-period component of seismic ground motion (e.g., long-span bridges and tall buildings).

Contribution of a new seismic amplification factor map approach for shakemaps improvement: the Croatia Mw=6.4 earthquake scenario.

<p>Estimation of site effects over large areas is a key-issue in a seismic risk mitigation perspective.</p><p>We prove here that the IGAG20 approach (Falcone et al., 2021), developed for the estimation of the stratigraphic Amplification Factors (AF) at a national scale for Italy, can be used in international context, as it is based on AF-V<sub>s30</sub> laws developed according to 40 geo-morphological clusters available globally after Iwahashi et al. (2018) and V<sub>s30 </sub>proxy laws after Mori et al. (2020).</p><p>The availability of AF maps is fundamental for the improvement of the estimates of surface shaking for the "shakemaps" produced after the seismic events, and for the consequent improvement of the preliminary estimates of coseismic effects (i.e. landslides and liquefaction) and damage of residential buildings.</p><p>The IGAG20 approach was implemented for evaluating the shaking maps for the recent Mw=6.4 Croatian seismic event, with a focus on the three most affected localities: Petrinjia, Sisak, and Glina. From the OpenQuake engine, Silva et al. (2014), a stochastic scenario analysis was performed and PGV and PGA shaking maps amplified with AF maps were produced. With the PGV map, landslide and liquefaction probability maps are produced respectively with the Nowicki et al. (2018) and Zhu et al. (2017) models. With the PGA map, a preliminary residential buildings damage estimation is produced and compared with the EMS98 damage distribution available from the grading maps produced by COPERNICUS (https://emergency.copernicus.eu/mapping/list-of-components/EMSR491 ). Finally, all the shaking maps are compared with USGS products (https://earthquake.usgs.gov/earthquakes/eventpage/us6000d3zh/executive).</p><p><strong>References </strong></p><p>Falcone, G., Mendicelli, A., Moscatelli, M., Romagnoli, G., Peronace, E., Naso, G., Acunzo G., Porchia, A., Tarquini, E., 2021. Seismic amplification maps of Italy based on site-specific microzonation dataset and one-dimensional numerical approach Eng. Geol. - Under review</p><p>Iwahashi, J., Kamiya, I., Matsuoka, M., Yamazaki, D., 2018. Global terrain classification using 280 m DEMs: segmentation, clustering, and reclassification. Prog. Earth Planet. Sci. https://doi.org/10.1186/s40645-017-0157-2</p><p>Mori, F., Mendicelli, A., Moscatelli, M., Romagnoli, G., Peronace, E., Naso, G., 2020. A new Vs30 map for Italy based on the seismic microzonation dataset. Eng. Geol. https://doi.org/10.1016/j.enggeo.2020.105745</p><p>Nowicki Jessee, M.A., Hamburger, M.W., Allstadt, K., Wald, D.J., Robeson, S.M., Tanyas, H., Hearne, M., Thompson, E.M., 2018. A Global Empirical Model for Near-Real-Time Assessment of Seismically Induced Landslides. J. Geophys. Res. Earth Surf. https://doi.org/10.1029/2017JF004494</p><p>Silva, V., Crowley, H., Pagani, M., Monelli, D., Pinho, R., 2014. Development of the OpenQuake engine, the Global Earthquake Model’s open-source software for seismic risk assessment. Nat. Hazards. https://doi.org/10.1007/s11069-013-0618-x</p><p>Zhu, J., Baise, L.G., Thompson, E.M., 2017. An updated geospatial liquefaction model for global application. Bull. Seismol. Soc. Am. https://doi.org/10.1785/0120160198</p>

Engineering-Geological Features Supporting a Seismic-Driven Multi-Hazard Scenario in the Lake Campotosto Area (L’Aquila, Italy)

This paper aims to describe the seismic-driven multi-hazard scenario of the Lake Campotosto artificial basin (Abruzzo Region, Central Italy), and it can represent a preparatory study for a quantitative multi-hazard analysis. A comprehensive multi-hazard scenario considers all the effects that can occur following the base ground shaking, providing a holistic approach to assessing the real hazard potential and helping to improve management of disaster mitigation. The study area might be affected by a complex earthquake-induced chain of geologic hazards, such as the seismic shaking, the surface faulting of the Gorzano Mt. Fault, which is very close to one of the three dams that form the Lake Campotosto, and by the earthquake-triggered landslides of different sizes and typologies. These hazards were individually and qualitatively analyzed, using data from an engineering-geological survey and a geomechanical classification of the rock mass. With regard to the seismic shaking, a quantitative evaluation of the seismic response of the Poggio Cancelli valley, in the northern part of Lake Campotosto, was performed, highlighting different seismic amplification phenomena due to morphologic and stratigraphic features. Some insights about the possible multi-hazard approaches are also discussed.

Methods and technologies of seismic strengthening of buildings with brick walls

Methods and instructions on the production technologies for the restoration and reinforcement of buildings with walls made of fired bricks, which have received various damages as a result of earthquakes, physical wear, and also have inconsistencies in space-planning and design solutions with the requirements of current regulatory documents, are given. The most typical types of damage to elements and structures of buildings as a result of earthquakes were identified and classified according to the results of analyzes of their consequences, in which the authors were directly involved (by the nature of their scientific and practical activities), as well as according to the analytical review of the relevant sources. The identification and compilation of classifications of the most common facts of inconsistency of space-planning and structural solutions with the requirements of the current design standards was carried out on the basis of the results of field inspections of the technical condition of numerous objects, the experience of which was accumulated by the authors over the past several years. Based on the results obtained, methods and technologies for seismic amplification of elements and structures of buildings have been developed, reflecting their features, composition and sequence of operations for the production of work, also based on the authors’ many years of experience in the implementation of similar developments, acquired during the implementation of a number of state scientific and technical programs, innovative projects and contractual work. For each of the considered cases and reinforcement options, the corresponding standards have been developed in relation to the labor intensity and cost of performing work, the recommended composition of the links and the corresponding standard set.