Anomalous propagation of refracted waves beneath the Orl¨ªk water reservoir, Czech Republic

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• 作者：Ji?¨ª M¨¢lek ; Old?ich Novotny ; Renata Ga?dov¨¢ and Libor ?anda
• 关键词：Vltava River ; Orl¨ªk reservoir ; refraction measurement ; travel time ; spectrum ; anomaly
• 刊名：Studia Geophysica et Geodaetica
• 出版年：2010
• 出版时间：July 2010
• 年：2010
• 卷：54
• 期：3
• 页码：389-401
• 全文大小：575.4 KB

文摘

The Orl¨ªk water reservoir was built on the Vltava River in the places where the river crosses the geological unit called the Central Bohemian Pluton. Previous geological studies have disclosed no significant lateral inhomogeneity or fault zone in the close vicinity of the reservoir. However, repeated levellings, performed there in the 1950s and 1960s, revealed a systematic subsidence of the Vltava River valley. Using these measurements, the idea of the tectonic origin of the valley was even formulated. Recent seismic observations have also attracted attention to this region. Namely, a macroseismically felt earthquake occurred there on January 13, 2007, and many weaker earthquakes have been recorded by local seismic networks since 1992. To increase the accuracy of locating these seismic events, recently we have carried out refraction measurements along a short profile across the Orl¨ªk reservoir. These authors smoothed the observed travel times and derived a 1-D velocity model of the shallow crustal structure for the Orl¨ªk region. In the present paper, using the same refraction measurements, we study some anomalies in wave propagation beneath the Orl¨ªk reservoir. In particular, it is shown that the passage of seismic waves beneath the reservoir leads to their time delays and spectral changes. Moreover, we have also recognised similar time delays in earlier data from the nearby international profile CEL09 in the places where the profile crosses the Orl¨ªk reservoir.