In the two last decades the microtremor H/V spectral ratio method has been widely used for site effect studies. Straightforward estimate of the site effect of sediments and low-cost measurements are the main advantages of mentioned method. In this research the use of microtremor measurements in estimation of site response have been investigated. In order to assessing the accuracy of the measurements and its application in site effect evaluation, a preliminary site response modeling was carried out using the numerical methods. The results showed that the H/V spectral ratio approach provides an acceptable means of site effect evaluation in study area.

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Evaluation of site response characteristics using microtremors

Following the incident in Petobo, Palu, liquefaction becomes an essential object for in-depth study. Based on soil investigation by the CPT (cone penetration test) in site soil test has been carried out at Jalan Taman Pancing, the area of Southern Bali Island was analyzed for liquefaction potential using geological interpretation and soil properties. Deterministic analysis using Stress Based Method, using the 2017 Seismic Hazard Map of Indonesia for Bali island where the earthquake acceleration reaches 0.4 - 0.5 g, meaning that Bali is highly vulnerable to earthquake, with the largest earthquake magnitude is the Mount Agung eruption measuring six on the Richter scale on May 18, 1963. The soil investigation shows that the layers of soil consist of sandy silt and silty clay at a depth between 0.5 - 12.0 m and 2 m water table, geological conditions with the Qa code alluvium deposits from ancient Buyan-Beratan Mountains. Deterministic analysis based on the CPT data and local geological conditions indicates that the thickness of the soil varies between 1.5 m and 9.5 m, while the safety factor of the liquefaction potential is in the critical conditions between 1.25 - 1.00.

/pdf/the-potential-of-liquefaction-disasters-based-on-the-usjvzusco2.pdf

The potential of liquefaction disasters based on the geological, CPT, and borehole data at Southern Bali Island

Equivalent linear ground response analysis is conducted to evaluate seismic site effects in Tehran, Iran. Recorded bedrock motions in acceleration stations within Tehran are scaled based on the pea...

Seismic site effect analysis for the city of Tehran using equivalent linear ground response analysis

As an important step in effectively reducing seismic risk and the vulnerability of the city of Mobarakeh to earthquakes, a site effect microzonation Study was conducted. Seismic hazard analysis for a return period of 475 years was carried out. Data from 10 borings was collected and analyzed, geophysical surveys were conducted and seismology and geoelectric measurements taken in more than 17 stations through out the city. The study area was divided into a grid of 500×500 m2 elements and the sub-surface ground conditions were classified into 5 representative geotechnical profiles. Electric resistivity was measured in close to 17 geotechnical boreholes and surface and sub-surface sediments were collected and analyzed. Site response analyses were carried out on each representative profile using 30 different base rock input motions. Distribution maps of site periods and peak ground acceleration and old and new texture buildings through out the city were developed, providing a useful basis for land-use planning in the city.

/pdf/soil-and-sediments-microzonation-for-evaluation-of-site-4g1m431hto.pdf

Soil and Sediments Microzonation for Evaluation of Site Effects on Earthquake Damages in Mobarakeh, Esfahan, Iran

Summary Nowadays in many site response analyses of alluvial, environment with shear wave velocity 600 m/sec < νs < 800 m/sec is considered as the seismic bedrock. Results of these analyses did not confirm those from empirical analyses based on the recording of microtremors or weak earthquake motions. Recently, effects of deep alluviums and contrast between geologic bedrock and alluviums are considered as a possible cause for this inconformity. This study examines the site effects of deep alluviums of Qom city. Qom is located at the northern margin of central Iran zone and on the Quaternary young alluviums. Based on the geoelectrical resistivity surveys, thickness of alluviums in some parts of the city is greater than 250m. Earlier empirical studies based on the recording of microtremors had shown that at the frequencies ranging from 0.6 to 1.2 Hz, a clear amplification can be seen in the studied alluviums. Amplification at these frequencies did * ﻂﺑار هﺪﻧرﺎﮕﻧ

https://journals.ut.ac.ir/article_35596_eaf805dbf231fc7137369c8382eadb43.pdf

Kenji Ishihara

Papers

Dynamic behaviour of soils soil amplification and soil structure interaction. Final report