A seismic swarm occurred southeast of King George Island,South Shetland Islands,Antarctica,between August 2020 and February 2021.This work intends to parameterize seismic events recorded by seismic station AM.R4DE2 fr...A seismic swarm occurred southeast of King George Island,South Shetland Islands,Antarctica,between August 2020 and February 2021.This work intends to parameterize seismic events recorded by seismic station AM.R4DE2 from 15 September to 31 October 2020.Using the localization methodology with a single station,the record of the entire period was analyzed manually to determine the local magnitude,hypocentral distance,epicentral distance,backazimuth,and location of the epicenter for each event.We could parameterize 6362 events,although we estimate the occurrence to be around 20000 for the period.The results suggest a magmatic origin for the swarm,supporting previous studies.Seismicity exhibited a southeastward migration away from King George Island,as indicated by a progressive increase in epicentral distance over time.Most events were classified as volcanic and volcano-tectonic,supporting a magmatogenesis hypothesis linked to the opening of Bransfield Ridge.展开更多
Multiple scattering of elastic waves in realistic media makes that averagefield intensities or energy densities follow diffusive processes.In such regime the successiveP to S energy conversions by distributed random i...Multiple scattering of elastic waves in realistic media makes that averagefield intensities or energy densities follow diffusive processes.In such regime the successiveP to S energy conversions by distributed random inhomogeneities give rise toequipartition which means that in the phase space the available elastic energy is distributedin averagewith equal amounts among the possible states of P and S waves.Insuch diffusive regime the P to S energy ratio equilibrates in an universal way independentof the particular details of the scattering.It has been demonstrated that averagingthe cross correlations at any two points of an elastic medium subjected to diffuse elasticwavefields leads to the emergence of the Green function,which is the wave fieldthat would be observed at one position if an impulsive load is applied at the other.Inthis work we study the problem of the retrieval of the 2D tensor elastodynamic Greenfunction in an infinite elastic space containing a circular cylinder inclusion.We illuminateisotropically the elastic spacewith plane waves.We assume the spectra for both Pand S waves uniform but such that the energy ratio ES/EP=(a/b)2,which is the onepredicted by equipartition theory in two-dimensions.We then show that the Fouriertransform of azimuthal average of the cross-correlation of motion between two pointswithin an elastic medium is proportional to the imaginary part of the exact Green tensorfunction between these points.The numerical results presented here point out thepossibility of detection and imaging of diffractors and resonant diffractors by crosscorrelation even in presence of attenuation exists.展开更多
文摘A seismic swarm occurred southeast of King George Island,South Shetland Islands,Antarctica,between August 2020 and February 2021.This work intends to parameterize seismic events recorded by seismic station AM.R4DE2 from 15 September to 31 October 2020.Using the localization methodology with a single station,the record of the entire period was analyzed manually to determine the local magnitude,hypocentral distance,epicentral distance,backazimuth,and location of the epicenter for each event.We could parameterize 6362 events,although we estimate the occurrence to be around 20000 for the period.The results suggest a magmatic origin for the swarm,supporting previous studies.Seismicity exhibited a southeastward migration away from King George Island,as indicated by a progressive increase in epicentral distance over time.Most events were classified as volcanic and volcano-tectonic,supporting a magmatogenesis hypothesis linked to the opening of Bransfield Ridge.
基金from project CGL2005-05500-C02-02/BTE from CICYT,Spainfrom the EU with FEDER+2 种基金the Research Team RNM-194 of Junta de Andaluc´ıa,Spainfrom CONACYT,Mexico,under grant NC-204from DGAPA-UNAM,Mexico,under grant IN114706,are gratefully acknowledged.
文摘Multiple scattering of elastic waves in realistic media makes that averagefield intensities or energy densities follow diffusive processes.In such regime the successiveP to S energy conversions by distributed random inhomogeneities give rise toequipartition which means that in the phase space the available elastic energy is distributedin averagewith equal amounts among the possible states of P and S waves.Insuch diffusive regime the P to S energy ratio equilibrates in an universal way independentof the particular details of the scattering.It has been demonstrated that averagingthe cross correlations at any two points of an elastic medium subjected to diffuse elasticwavefields leads to the emergence of the Green function,which is the wave fieldthat would be observed at one position if an impulsive load is applied at the other.Inthis work we study the problem of the retrieval of the 2D tensor elastodynamic Greenfunction in an infinite elastic space containing a circular cylinder inclusion.We illuminateisotropically the elastic spacewith plane waves.We assume the spectra for both Pand S waves uniform but such that the energy ratio ES/EP=(a/b)2,which is the onepredicted by equipartition theory in two-dimensions.We then show that the Fouriertransform of azimuthal average of the cross-correlation of motion between two pointswithin an elastic medium is proportional to the imaginary part of the exact Green tensorfunction between these points.The numerical results presented here point out thepossibility of detection and imaging of diffractors and resonant diffractors by crosscorrelation even in presence of attenuation exists.
