NONLINEAR PHENOMENA IN VOLCANIC TREMOR

Speaker: CHOLISINA ANIK PERWITA
Date:2012/12/20

Abstract

Tremor is a persistent ground vibration that is observed only near an active volcano and is often accompanied by evidence of subterranean magma motion. Some proposed tremor generating such as resonance of “rock” laminae adjacent to magma conduits, “flow crises” caused by supersonic flow of gase, the flashing of water to steam and jerky propagation of magma-filled crack can not explain the tremor in non linear behaviour such as change frequency from harmonic to broadband. Julian (1994) proposed model of nonlinear oscillators called flow induced oscillation. Phenomena of flow induced oscillation also can found in mammalian circulatory system (Korotkoff Sound). In case of volcano system, tremor oscillation are exited by nonlinear instabilities that arise when fluid flows through a constricted channel with deformable walls. This system’s behaviour depend on it’s geometry, the pressure difference driving fluid and also the physical properties of the fluid and the wall rocks. Non ocillators change from periodic to “chaotic” behavior in response to changes in their physical parameters. There are several ways that systems can make this transition, but the commonest route is the “subharmonic period-doubling cascade”. Period doubling can form if the sytem reach it’s critical point that make frequency period become double repeatedly and incresing without limit in the end. Period doubling modeling was done without considering any resonce. Thus, it is not necessary to invoke accoustic resonace in generating tremor. Phase space map was conduct in order to describe behaviour of the system. Using three dimension that corelate with three parameter involve in flow induce system, showed that attractor type in phase space map similiar with Rossler type.

 

References

Julian, B. R., 1994. Volcanic Tremor: Nonlinear Excitation by Fluid Flow. J. Geophys. Res. 99, 11859–11877.

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Julian, B.R., 2000. Period doubling and other nonlinear phenomena in volcanic earthquakes and tremor. J. Volcanol. Geotherm. Res. 101, 19–26.

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