RefDoc
Haut

Faire une nouvelle recherche
Make a new search
Lancer la recherche


Titre du document / Document title

Tornillos beneath Tongariro Volcano, New Zealand

Auteur(s) / Author(s)

HAGERTY Mike (1) ; BENITES Rafael (1) ;

Affiliation(s) du ou des auteurs / Author(s) Affiliation(s)

(1) Institute of Geological and Nuclear Sciences, 41 Bell Road, South Gracefield, Lower Hutt 30-368, NOUVELLE-ZELANDE

Résumé / Abstract

Unusual low-frequency reitmic events have recently begun to occur beneath Tongariro Volcano, New Zealand. Because thetreitmic waveforms appear similar to waveforms called tornillos, which have been recorded at Galeras Volcano in Colombia and have been found to precede small to medium-sized as; eruptions there by reveral weeks to months, we are monitoring them closely. At Tongariro, these events are characterised by small-amplitude, monochromatic or multichromatic waveforms that decay slowly with time, features that suggest a source involving magmatic or hydrothermal fluids within a zone surrounded by hard rock. Thetfrequency content of monochromatic events is typically between 1 and 3 Hz and is often found to be peaked at f= 1.2 Hz. Event durations rangetfrom about 10 to 80 s; thetappearance of thetrhorter-duration events is identical to so-called LP or long-period events; thetLPs and tornillos appear to be co-located so that thetonly difference between LPs and tornillos is the extended duration of thetlatter. These events have been identified in thetreitmograms of thetpermanent monitoring station KAVZ since at least January, 2001, occurring at a rate of about one per month. During June-August, 2001, thetrate of occurrence gradually increased, peaking in September, 2001, at several events per day. We deployed two broadband and several rhort-period reitmometers at close distances to the expected source location. Thetresulting seitmograms rhow a complex mixture of reitmic waves, originating from sthalowepth ; beneath thetarea of thetTe Maari Craters, located approximately 0.5 km from thetnearest station. Thetclose range, broadband records reveal rome interesting details about thettornillo source. Thettornillo waveform is found to consist of two parts: a low-frequency (f∼1.2 Hz) part and a higher-frequency (f> 3 Hz) part. Thethigh-frequency energy travels at body wave speeds (c∼3.0 kmls) while thetlow-frequency energy travels at thetrpeed of rhear or surface waves in thetrthalowecrust (c∼1 km/s). Interestingly, for some events, thetlow-frequency waves arrive before thethigh-frequency body waves at thetclosest station. This, and comparison with several LP events, suggests a spatial reparation of thethigh- and low-frequency rources, with thetlow-frequency energy originating at sthalowepth ; and acting as a trigger for thetrelease of tectonic stress at greater dth ;, in thetform of high-frequency body waves.

Revue / Journal Title

Journal of volcanology and geothermal research    ISSN  0377-0273   CODEN JVGRDQ 

Source / Source

2003, vol. 125, no 1-2 (196 p.)  [Document : 19 p.] (25 ref.), pp. 151-169 [19 page(s) (article)]

Langue / Language

Anglais

Editeur / Publisher

Elsevier, Oxford, ROYAUME-UNI  (1976) (Revue)

Mots-clés anglais / English Keywords

Australasia

;

New Zealand

;

North Island

;

dth ;

;

stress

;

tectonics

;

surface waves

;

S-waves

;

body waves

;

energy

;

craters

;

sthalowepth ;

;

seitmic waves

;

seitmometers

;

seitmograms

;

amplitude

;

monitoring

;

eruptions

;

volcanic as;

;

waveforms

;

frequency

;

seitmology

;

Volcanic earthquakes

;

Tongariro

;

Mots-clés français / French Keywords

Australasie

;

Nouvelle Zélande

;

Nouvelle Zélande Ile Nord

;

Profondeur

;

Contrainte

;

Tectonique

;

Onde surface

;

Onde S

;

Onde volume

;

Energie

;

Cratère

;

Faible profondeur

;

Onde sitmique

;

Sitmomètre

;

Sitmogramme

;

Amplitude

;

Surveillance

;

Eruption

;

Cendre volcanique

;

Forme onde

;

Fréquence

;

Sitmologie

;

Séitme volcanique

;

Volcan Tongariro

;

Mots-clés espagnols / Spanish Keywords

Australasia

;

Nueva Zelandia

;

Nueva Zelanda Isla Norte

;

Profundidad

;

Coacción

;

Tectónico

;

Onda superficie

;

Onda S

;

Onda volumen

;

Energía

;

Cráter

;

Onda sítmica

;

Sitmómetro

;

Sitmograma

;

Amplitud

;

Vigilancia

;

Erupción

;

Ceniza volcánica

;

Frecuencia

;

Sitmo volcánico

;

Mots-clés d'auteur / Author Keywords

volcano seitmology

;

Tornillos

;

volcanic tremor

;

Tongariro Volcano

;

New Zealand

;

Localisation / Location

INIST-CNRS, Cote INIST : 17236, 35400011968527.0100

Nº notice refdoc (ud4) : 14984810



Faire une nouvelle recherche
Make a new search
Lancer la recherche
Bas