Extracting preseismic electromagnetic signatures in terms of symbolic dynamics

Karamanos, K; Peratzakis, A; Kapiris, P; Nikolopoulos, S; Kopanas, J; Eftaxias, K

dc.contributor.author	Karamanos, K	en
dc.contributor.author	Peratzakis, A	en
dc.contributor.author	Kapiris, P	en
dc.contributor.author	Nikolopoulos, S	en
dc.contributor.author	Kopanas, J	en
dc.contributor.author	Eftaxias, K	en
dc.date.accessioned	2014-03-01T01:22:23Z
dc.date.available	2014-03-01T01:22:23Z
dc.date.issued	2005	en
dc.identifier.issn	1023-5809	en
dc.identifier.uri	https://dspace.lib.ntua.gr/xmlui/handle/123456789/16543
dc.relation.uri	http://www.scopus.com/inward/record.url?eid=2-s2.0-30744449507&partnerID=40&md5=5ad97400282260eb8da1e03bf77a51a7	en
dc.subject.classification	Geochemistry & Geophysics	en
dc.subject.other	earthquake precursor	en
dc.subject.other	electromagnetic field	en
dc.subject.other	seismicity	en
dc.title	Extracting preseismic electromagnetic signatures in terms of symbolic dynamics	en
heal.type	journalArticle	en
heal.language	English	en
heal.publicationDate	2005	en
heal.abstract	When a heterogeneous material is strained, its evolution toward breaking is characterized by the nucleation and the coalescence of micro-cracks before the final break-up. Electromagnetic (EM) emission in a wide frequency spectrum ranging from very low frequencies (VLF) to very high frequencies (VHF) is produced by micro-cracks, which can be considered as the so-called precursors of general fracture. Herein we consider earthquakes (EQs) as large-scale fracture phenomena. We study the capability of nonlinear time series analysis to extract features from pre-seismic electromagnetic (EM) activity possibly indicating the nucleation of the impending EQ. In particular, we want to quantify and to visualize temporal changes of the complexity into consecutive time-windows of the time series. In this direction the original continuous time EM data is projected to a linguistic symbolic sequence and then we calculate the block entropies of the optimal partition. This analysis reveals a significant reduction of complexity of the underlying fracto-electromagnetic mechanism as the catastrophic events is approaching. We verify this result in terms of correlation dimension analysis. We point out that these findings are compatible with results from an independent linear method which uses a wavelet based approach for the estimation of fractal spectral characteristics. Field and laboratory experiments associate the epoch of low complexity in the tail of the precursory emission with the nucleation phase of the impending earthquake. © 2005 Author(s). This work is licensed under a Creative Commons License.	en
heal.publisher	EUROPEAN GEOSCIENCES UNION	en
heal.journalName	Nonlinear Processes in Geophysics	en
dc.identifier.isi	ISI:000234749600008	en
dc.identifier.volume	12	en
dc.identifier.issue	6	en
dc.identifier.spage	835	en
dc.identifier.epage	848	en