What Can Be Concluded about Seismic History from Broken and Unbroken Speleothems?

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Publication Date

January 2004

Abstract

Is it really plausible that earthquakes break speleothems? May unbroken speleothems prove that no strong earthquake has ever occurred during a certain period of time? The mechanical behaviour of speleothems has been investigated through static bending tests performed on stalactites and soda straws. These tests give an indication not only of the mean tensile resistance, but also — more importantly — of its variation. In fact, it is this variation that makes it difficult to estimate the acceleration necessary to break an individual speleothem. That is why a statistical approach is mandatory. The potentially most vulnerable unbroken as well as broken stalactites were measured in a pilot cave (Milandre, Switzerland). Four classes of stalactites were defined, according to their shapes. For each of these classes, a vulnerability curve (probability of breaking as a function of peak ground acceleration) was obtained by means of a Monte Carlo simulation. Dynamic amplification as well as heterogeneity of bending resistance within each speleothem were taken into account. Finally, an original statistical approach, valid for incomplete and imprecise data, was developed. This approach allowed to estimate the probability that at least one moderate earthquake has occurred in the past.

Keywords

Long Return Periods, Paleoseismicity, Speleothems, Stalactites, Vulnerability

Document Type

Article

Notes

Journal of Earthquake Engineering, Vol. 8, no. 3 (2004).

Identifier

SFS0069941_00001

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