Dynamic characteristics of built heritage using ambient noise recordings

Abstract

The paper addresses the investigation of the dynamic characteristics of a case study, the Egyptian church of Abu serga. To this aim some in situ investigations have been conducted and related results are discussed. The paper presents interesting and innovative aspects, mainly related to the characteristics of the church investigated, covering a lack of knowledge in the scientific literature due to the typology of the church. The integrated geotechnical and geophysical investigation techniques assessed the level of seismic and other geo-environmental risks that Abu serga church suffers from. It suffers multiple Geo-environmental hazards. The main objectives of this pilot study are as follows: (1) Identifying the shear velocity Vs analysis profile of the subsoil and also the resonant frequency of soil and the historical building of Abu serga church using ambient noise recordings (microtremors) to assess the level of seismic and other geo-environmental hazards. (2) Understanding the damage to the historic building caused by the recent earthquakes. (3) Offering technical support and advice on intervention retrofitting for the historic damaged structure.In this study, ambient noise recordings have been processed through horizontal to vertical spectral ratios to examine the main frequencies and to examine whether the building has its main frequency close to that of the soil in order to identify potential resonance phenomena. Numerous ambient noise recordings were recorded on the soil, in the basement, and at each floor of the buildings.This study suggests moderate level of earthquake activity at Abu serga church and is in a good agreement with the fact that “Egypt is a part of the stable African Shield”, but the existence of old structures such as the Abu serga church may reduce the ability to resist any earthquake shaking.