Modeling stratigraphic structure of Menemen Plain-Izmir/Turkey by microgravity, passive seismic methods and examining its behavior under earthquake effect

Considering the processes that are effective in the formation of the geometry of the sedimentary basin, using stratigraphic information obtained from a small number of boreholes may be insufficient for the modeling and interpretation of a very large area for construction purposes. Moreover, if the behavior of this large area under the effect of earthquake needs to be modeled, the number of boreholes and the geometry of their distribution across the area are very important. Is it always possible to obtain data by a sufficient number of boreholes with sufficient depths in all kinds of regions? A stratigraphic sequence can be defined at the end of the analysis of microtremor data and joint evaluation of the findings and microgravity data set obtained together. Defining the related stratigraphic structure is the input parameter for modeling the soil behavior based on an existing earthquake record. This study aims to model the behavior of the stratigraphy of the Menemen Plain and its surroundings under a possible earthquake force. Due to the active tectonic regime of Western Anatolia, there are many records about the destructive earthquakes in Menemen Plain, Izmir and its surroundings in both historical and instrumental records. From this perspective, a basic data set was created for the study area using microgravity and microtremor methods. S-Wave Velocity depth sections were obtained from the forward and inverse solutions of Horizontal/Vertical Spectral Ratio (HVSR) curves obtained from microtremor method evaluations. Density values were calculated from these S-wave velocity data obtained with the help of empirical equations. For the 4 profiles determined in the study area, the profile sections were drawn using Bouguer map and gravity models of these profiles were prepared. The gravity models obtained were interpreted by considering the 1D S-Wave Velocity sections and the geology of the region in combination, and the stratigraphic features of the Menemen Plain were determined in 2D. In this study, the results obtained using microtremor and microgravity methods and the efficiency of the models obtained from these results were investigated across Menemen Plain in the Western Anatolia Region based on the limited borehole data available. Finally, possible soil responses during an earthquake scenario were calculated based on the earthquake in Akhisar/Manisa/Turkey on 18.02.2020 at 16:09:22 (GMT), Mw = 5.2, 39.1060(0) N-27.8747 degrees E, for the midpoints of the 4 profiles that were modeled. (C) 2020 Elsevier B.V. All rights reserved

Non-linear soil behavior analysis of collapsed building after the Samos Earthquake (30.10.2020 Mw=6.9)

Samos Earthquake(30.10.2020, Mw =6.9) had catastrophic effects on theBayraklı district (withinBornova Plain) of Izmir. 17 buildings completely collapsed, almost thousand building were heavily damaged due to the earthquake.Bornova Plain isan east-west trending tectonic depression developed within thehorst-graben system ofWestern Anatolia. TheBornova Plain was filled with the alluvium brought by the short, seasonal streams that reach the plain from the surrounding high masses. Seasonal changes in the flow regimes of these streams have created an inhomogeneous accumulation in horizontal and vertical directions. This thick accumulation of low S-wave velocity and intensity will amplify the earthquake waves. However, it should be noted that the basin topography of the plain will also have unwanted effects on earthquake waves.3513 strong ground motion station located in theBayraklı district and on the coast of Izmir Bay measured the peak acceleration value(PGA) of the earthquake as0.108 g. Although the building stock ofİzmir does not differ from place to place, various analyzes have been made in the areas where the buildings collapsed after the earthquake was located to investigate the reasons for the collecting of demolitions in asingle area. In this context, an earthquake simulation was carried out for the soil under a collapsed building. In designing this earthquake simulation; Earthquake dataof 3513 strong-motion station, soil-bedrockmodel of 3513 strong-motion

Soil characterization of Bornova Plain (Izmir, Turkey) and its surroundings using a combined survey of MASW and ReMi methods and Nakamura's (HVSR) technique

Structural damage which occurs during earthquakes is related to both the soil dynamic behavior attributes and soil response spectrums. Therefore, soil characterization based of S-wave velocity (Vs) is one of the prime factors to estimate damage and hazards. In this study, multi-channel analysis of surface waves (MASW) and refraction microtremor (ReMi) methods have been applied to estimate Vs values of the area located east of Izmir Bay. Based on the estimated Vs values, two- and three-dimensional shear-wave velocity and the maximum shear modulus maps at various depths down to 50m were prepared. To study the relationship between the predominant period of the soil and shear-wave velocity values, a horizontal-to-vertical (H/V) spectral ratio method using Nakamura's technique has been applied. Groundwater level, standard penetration test (SPT-N30) and Poisson ratio values were also obtained from previous geotechnical borehole data in the study area. In addition, we calculated building periods using the empirical relationship between height (or number of floors) of buildings and predominant period of the buildings to examine soil-structure resonance. According to the National Earthquake Hazard Reduction Program (NEHRP; 1997) soil classification, the study site consists of B-, C- and F-type soils. Risk maps were created using dynamic properties of the soil