Strong Motion Networks: A Tool For The Assessment of Earthquake Response of Historical Monuments

Strong motion networks installed in two historical monuments in Istanbul, Turkey, namely in Hagia Sophia Museum and in Süleyrnaniye Mosque, yielded valuable information regarding their time-domain and frequency-domain dynamic characteristics. The existing information was enhanced by recordings obtained during the recent August 17, 1999, Kocaeli (M_w=7.4) and November 12, 1999, Düzce, Turkey (M_w=7.2) earthquakes and during the following aftershock activity. Analysis of data yielded following results: The two buildings with similar structural support systems have different vibration characteristics. There is an earthquake specific variation of modal frequencies in the two structures which exists during low amplitude events as well. Local problems in terms of excessive vibrations exist in the southwest main pier of Hagia Sophia and possibly in the west main arch of Süleyrnaniye. Significant vertical vibrations at the crowns of the east and west main arches in Hagia Sophia are probably indicating locations where most of the damage are to be expected during a major earthquake close to Istanbul. The strong motion accelerometer networks are valuable tools for monitoring of historical structures and help to identify potential problems and/or to explain past/present structural problems. It is expected that such networks will become a standard tool for investigations towards the preservation of historical buildings in seismic areas in the future.