The earthquake monitoring for Kuzuryu dam has been conducted since its completion. Due to the aging deterioration and following update of the monitoring system, the current system is arranged to the underground powerhouse in addition to the dam crest and both dam abutments. Around 200 earthquake data accumulated so far clarify the dynamic behavior of the dam and its foundation. The dynamic amplification characteristics of the dam and its abutments reflect the characteristics of these materials and configurations. The possible influence on the monitored acceleration due to the existence of the underground powerhouse nearby the dam is examined referring to the numerical simulation of the seismic propagation as well as the frequency analysis. The disturbance due to nearby existing underground structure on the seismic wave amplification is confined in its surrounding area and negligible in other part of the dam foundation.

1 Introduction

Propagation characteristics of the dam foundation are critical parameters to evaluate the seismicity for the assessment of the anti-seismic performance of dams and these appurtenant structures. 3-D numerical model consisting of a dam, foundation and a reservoir is frequently utilized to examine its characteristics. However simplification of the model and/ or uncertainties of material properties always claim the verification on the applicability of the model. The reproduction analysis of the dam behavior during earthquakes is quite adequate for this purpose.

The earthquake monitoring is recently a standard menu for the dam. It has been scarcely conducted in the existing dams aged more than several decades. Devices for the earthquake monitoring have been newly arranged in some of these. The monitoring of the dam behavior is usually focused, resulting that the arrangement of the devices are limited only on the crest and lower elevation of the dam. A few attentions are paid to the amplification characteristics of the dam foundation. Therefore, very few data are available to the verification above-mentioned.

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