MULTIFRACTAL ANALYSIS OF MOUNT St. HELENS SEISMICITY AS A TOOL FOR IDENTIFYING ERUPTIVE ACTIVITY

We present a multifractal analysis of Mount St. Helens seismic activity during 1980–2002. The seismic time distribution is studied in relation to the eruptive activity, mainly marked by the 1980 major explosive eruptions and by the 1980–1986 dome building eruptions. The spectrum of the generalized fractal dimensions, i.e. Dq versus q, extracted from the data, allows us to identify two main earthquake time distribution patterns. The first one exhibits a multifractal clustering correlated to the intense seismic swarms of the dome building activity. The second one is characterized by an almost constant value of Dq ≈ 1, as for a random uniform distribution. The time evolution of Dq (for q = 0.2), calculated on a fixed number of events window and at different depths, shows that the brittle mechanical response of the shallow layers to rapid magma intrusions, during the eruptive periods, is revealed by sharp changes, acting at a short time scale (order of days), and by the lowest values of Dq (≈ 0.3). Conversely, for deeper earthquakes, characterized by intense seismic swarms, Dq do not show obvious changes during the whole analyzed period, suggesting that the earthquakes, related to the deep magma supply system, are characterized by a minor degree of clustering, which is independent of the eruptive activity.

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Numerical modelling of the crack-pore interaction and damage evolution behaviour of rocklike materials with pre-existing cracks and pores

International Journal of Damage Mechanics ◽

10.1177/1056789520983874 ◽

2020 ◽

pp. 105678952098387

Author(s):

PLP Wasantha ◽

D Bing ◽

SQ Yang ◽

T Xu

Keyword(s):

Principal Stress ◽

Damage Evolution ◽

Shear Failure ◽

Mechanical Response ◽

Distribution Patterns ◽

Stress Distributions ◽

Compressive Stresses ◽

Major Principal Stress ◽

The Right ◽

Macroscopic Failure

The combined effect of pre-existing cracks and pores on the damage evolution behaviour and mechanical properties of rocklike materials under uniaxial compression was numerically studied. Simulations of cracks and pores alone showed that increasing crack length and pore diameter decrease uniaxial compressive strength (UCS) and elastic modulus. Subsequent simulations considered two types of combinations of pre-existing cracks and pores – two cracks either side of a centric pore, and two pores either side of a centric crack – and the distance between cracks and pores was changed. In the case of two cracks at either side of the pore, UCS increased only slightly when the distance between the cracks and pore was increased. This was attributed to the more profound effect of the presence of the pore on UCS, and was confirmed by the progressive crack development characteristics and the major principal stress distribution patterns, which showed that the cracks initiated from the tips of the two pre-existing cracks made little or no contribution to the ultimate macroscopic failure. In contrast, models with two pores at either side of a centric crack showed a marked dependency of UCS on the distance between the pores and the crack. Cracks propagating from pre-existing pores made a greater contribution to the ultimate macroscopic failure when the pores were close to the centric crack and the effect gradually diminished with increasing space between pre-existing pores and the centric crack. Major principal stress distributions showed an asymmetric mobilisation of compressive stresses at the right and left sides of the two pores, favouring macroscopic shear failure when they were close to the centric crack which had led to a lower UCS. Overall, this study presents some critical insights into crack-pore interaction behaviour and the resulting mechanical response of rocklike materials to assist with the design of rock structures.

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Multifractal analysis of the rainfall time distribution on the metropolitan area of Barcelona (Spain)

Meteorology and Atmospheric Physics ◽

10.1007/s00703-013-0256-6 ◽

2013 ◽

Vol 121 (3-4) ◽

pp. 181-187 ◽

Cited By ~ 18

Author(s):

R. Rodríguez ◽

M. C. Casas ◽

A. Redaño

Keyword(s):

Metropolitan Area ◽

Time Distribution ◽

Multifractal Analysis

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Monitoring eruptive activity at Mount St. Helens with TIR image data

Geophysical Research Letters ◽

10.1029/2005gl024112 ◽

2005 ◽

Vol 32 (19) ◽

pp. n/a-n/a ◽

Cited By ~ 29

Author(s):

R. G. Vaughan ◽

S. J. Hook ◽

M. S. Ramsey ◽

V. J. Realmuto ◽

D. J. Schneider

Keyword(s):

Image Data ◽

Eruptive Activity ◽

Mount St Helens

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Numerical Methods of Multifractal Analysis in Information Communication Systems and Networks

Integrated Models for Information Communication Systems and Networks ◽

10.4018/978-1-4666-2208-1.ch002 ◽

2013 ◽

pp. 16-46

Author(s):

Oleg I. Sheluhin ◽

Artem V. Garmashev

Keyword(s):

Communication Systems ◽

Multifractal Analysis ◽

Fractal Dimensions ◽

Multifractal Spectrum ◽

Telecommunication Networks ◽

Information Communication ◽

Novel Approach ◽

Wavelet Transform Modulus Maxima ◽

Modulus Maxima ◽

Development Methods

In this chapter, the main principles of the theory of fractals and multifractals are stated. A singularity spectrum is introduced for the random telecommunication traffic, concepts of fractal dimensions and scaling functions, and methods used in their determination by means of Wavelet Transform Modulus Maxima (WTMM) are proposed. Algorithm development methods for estimating multifractal spectrum are presented. A method based on multifractal data analysis at network layer level by means of WTMM is proposed for the detection of traffic anomalies in computer and telecommunication networks. The chapter also introduces WTMM as the informative indicator to exploit the distinction of fractal dimensions on various parts of a given dataset. A novel approach based on the use of multifractal spectrum parameters is proposed for estimating queuing performance for the generalized multifractal traffic on the input of a buffering device. It is shown that the multifractal character of traffic has significant impact on queuing performance characteristics.

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