Variation of ground-motion amplification and structural dynamic characteristics of Amman citadel |
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| Authors: | Mohammad Fandi Tawfiq Alyazjeen |
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| Institution: | 1. Natural Resources Authority (NRA), Jordan Seismological Observatory & Geophysical Studies, P.O. Box 7, 11118, Amman, Jordan
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| Abstract: | Structural remains of the site refer to clear evidence of large historical earthquakes that strongly affected the site during the last 2,000 years. In this work, we present a study of dynamic behavior of Jabal Al-Qalaa site as well as the dynamic behavior of some archeological remaining structures on the site using the free oscillation of surface geology and structures. In this study, seven ground records were obtained along approximately east–west profile, crossing the top of the hill zone. Structural records were obtained at three selected structures following administrative requirements. All structural records were conducted at the top level of each structure using three components seismometer of 2 Hz free oscillation. Horizontal sensors were oriented with respect to the longitudinal and transverse direction of structural horizontal projection. Used orientations are essential for obtaining both structural fundamental modes in the longitudinal and transverse directions. Moreover, damping factors for each horizontal fundamental mode were calculated based on the obtained FFT spectrums of each orientation using half-width band method. Analysis shows that all inspected structures in this study are of high frequency. Interesting results of records obtained at the Umayyad Alcazar, relatively low damping factor as well as sharp fundamental modes in its both longitudinal and transverse directions are recorded at this well-preserved old historical structure. Free-field records were conducted along approximately E-W profile crossing the top of the hill. The purpose of this methodology is to identify the variation of H/V amplification along with, and to find out the topographical effect of this convex geological feature. Obtained H/V ground resonance dominant modes as well as the site amplification reflect well the topographical effect of the citadel hill zone. Amplification gradually increases to reach 4.5 at the top of the hill. |
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