<?xml version="1.0" encoding="ISO-8859-1"?><article xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<front>
<journal-meta>
<journal-id>0016-7169</journal-id>
<journal-title><![CDATA[Geofísica internacional]]></journal-title>
<abbrev-journal-title><![CDATA[Geofís. Intl]]></abbrev-journal-title>
<issn>0016-7169</issn>
<publisher>
<publisher-name><![CDATA[Universidad Nacional Autónoma de México, Instituto de Geofísica]]></publisher-name>
</publisher>
</journal-meta>
<article-meta>
<article-id>S0016-71692005000100022</article-id>
<title-group>
<article-title xml:lang="en"><![CDATA[Seismic survey in southeastern Socorro Island: Background noise measurements, seismic events, and T phases]]></article-title>
</title-group>
<contrib-group>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Valenzuela]]></surname>
<given-names><![CDATA[Raúl W.]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Galindo]]></surname>
<given-names><![CDATA[Marta]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Pacheco]]></surname>
<given-names><![CDATA[Javier F.]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Iglesias]]></surname>
<given-names><![CDATA[Arturo]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Terán]]></surname>
<given-names><![CDATA[Luis F.]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Barreda]]></surname>
<given-names><![CDATA[José L.]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Coba]]></surname>
<given-names><![CDATA[Carlos]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
</contrib-group>
<aff id="Af1">
<institution><![CDATA[,Universidad Nacional Autónoma de México Instituto de Geofísica Departamento de Sismología]]></institution>
<addr-line><![CDATA[México D. F.]]></addr-line>
<country>Mexico</country>
</aff>
<aff id="Af2">
<institution><![CDATA[,Comprehensive Nuclear-Test-Ban Treaty Organization International Monitoring System Division Hydroacoustic Monitoring Section]]></institution>
<addr-line><![CDATA[Vienna Austria]]></addr-line>
</aff>
<aff id="Af3">
<institution><![CDATA[,Benemérita Universidad Autónoma de Puebla Facultad de Ingeniería ]]></institution>
<addr-line><![CDATA[Puebla Pue]]></addr-line>
<country>Mexico</country>
</aff>
<pub-date pub-type="pub">
<day>00</day>
<month>03</month>
<year>2005</year>
</pub-date>
<pub-date pub-type="epub">
<day>00</day>
<month>03</month>
<year>2005</year>
</pub-date>
<volume>44</volume>
<numero>1</numero>
<fpage>22</fpage>
<lpage>38</lpage>
<copyright-statement/>
<copyright-year/>
<self-uri xlink:href="http://www.scielo.org.mx/scielo.php?script=sci_arttext&amp;pid=S0016-71692005000100022&amp;lng=en&amp;nrm=iso"></self-uri><self-uri xlink:href="http://www.scielo.org.mx/scielo.php?script=sci_abstract&amp;pid=S0016-71692005000100022&amp;lng=en&amp;nrm=iso"></self-uri><self-uri xlink:href="http://www.scielo.org.mx/scielo.php?script=sci_pdf&amp;pid=S0016-71692005000100022&amp;lng=en&amp;nrm=iso"></self-uri><abstract abstract-type="short" xml:lang="en"><p><![CDATA[ABSTRACT We carried out a seismic survey and installed five portable, broadband seismometers in the southeastern corner of Socorro Island during June 1999. Power spectral densities for all five sites were relatively noisy when compared to reference curves around the world. Power spectral densities remain constant regardless of the time of day, or the day of the week. Cultural noise at the island is very small. Quiet and noisy sites were identified to determine the best location of the T phase station to be installed jointly by the Universidad Nacional Autónoma de México and the Comprehensive Nuclear-Test-Ban Treaty Organization. During the survey six earthquakes were recorded at epicentral distances between 42 km and 2202 km, with magnitudes between 2.8 and 7.0. Two small earthquakes (M  c = 2.8 and 3.3) occurred on the Clarión Fracture Zone. The four largest and more distant earth-quakes produced T waves. One T wave from an epicenter near the coast of Guatemala had a duration of about 100 s and a frequency content between 2 and 8 Hz, with maximum amplitude at about 4.75 Hz. The Tehuacán earthquake of June 15, 1999 (M  w = 7.0) produced arrivals of P- Tand S -- T waves, with energy between 2 Hz and 3.75 Hz. The earthquake occurred inland within the subducted Cocos plate at a depth of 60 km; a significant portion of the path was continental. Seismic P and S waves probably propagated upward in the subducted slab, and were converted to acoustic energy at the continental slope. Total duration of the T phase is close to 500 s and reaches its maximum amplitude about 200 s after the P - T arrival. The T wave contains energy at frequencies between 2 and 10 Hz and reaches its maximum amplitude at about 2.5 Hz. T phases were also recorded from two earthquakes in Guerrero, Mexico and in the Rivera Fracture Zone.]]></p></abstract>
<abstract abstract-type="short" xml:lang="es"><p><![CDATA[RESUMEN En junio de 1999 instalamos cinco sismómetros portátiles de banda ancha en el sureste de la Isla Socorro. Se encontró que las densidades espectrales de potencia en los cinco sitios son relativamente ruidosas en comparación con las curvas mundiales de referencia. Este resultado concuerda con observaciones realizadas en otras islas pequeñas. Las densidades espectrales de potencia permanecen constantes sin importar la hora del día o el día de la semana. Los efectos del ruido cultural en la isla son muy pequeños. Se identificaron los sitios con el mayor y el menor ruido. Esta información servirá para determinar la ubicación de la estación de fase T que será instalada conjuntamente por la Universidad Nacional Autónoma de México y la Organización del Tratado para la Prohibición Completa de Ensayos Nucleares. Durante el periodo de estudio se registraron seis sismos. Estos ocurrieron a distancias epicentrales entre 42 y 2202 km y tuvieron magnitudes entre 2.8 y 7.0. Dos sismos pequeños (Mc = 2.8 y 3.3) y cercanos ocurrieron en la Zona de Fractura de Clarión. Los cuatro eventos más grandes y más lejanos generaron ondas T. La onda T producida por un temblor cerca de la costa de Guatemala tuvo una duración de alrededor de 100 s y frecuencias entre 2 y 8 Hz, con un máximo en su amplitud aproximadamente a 4.75 Hz. El terremoto de Tehuacán del 15 de junio de 1999 (Mw = 7.0) generó ondas P -- T y S -- T, ambas con energía entre 2 y 3.75 Hz. Dicho sismo ocurrió dentro de la placa subducida de Cocos a una profundidad de 60 km y el epicentro se localizó lejos de la costa del océano Pacífico. Esto implica que un segmento largo de la trayectoria fue recorrido por tierra. Inicialmente la energía viajó en forma de ondas sísmicas P y S, las cuales probablemente se propagaron por dentro de la placa subducida, y éstas después se convirtieron a energía acústica al pasar de la tierra al agua en el talud continental frente a la costa del océano Pacífico. La duración total de la fase T es cercana a los 500 s y alcanza su amplitud máxima alrededor de 200 s después de la llegada de la onda P -- T. La fase T tiene energía en frecuencias entre 2 y 10 Hz y alcanza su amplitud máxima a aproximadamente 2.5 Hz. También se registraron las fases T producidas por un sismo en el estado de Guerrero, México y otro en la Zona de Fractura de Rivera.]]></p></abstract>
<kwd-group>
<kwd lng="es"><![CDATA[Tratado para la Prohibición Completa de Ensayos Nucleares (TPCEN)]]></kwd>
<kwd lng="es"><![CDATA[canal de fijación y determinación de la distancia por sonido (SOFAR)]]></kwd>
<kwd lng="es"><![CDATA[explosiones nucleares]]></kwd>
<kwd lng="es"><![CDATA[Isla Socorro]]></kwd>
<kwd lng="es"><![CDATA[fases T]]></kwd>
<kwd lng="es"><![CDATA[Zona de Fractura de Clarión]]></kwd>
<kwd lng="es"><![CDATA[Zona de Fractura de Rivera]]></kwd>
<kwd lng="es"><![CDATA[océano Pacífico]]></kwd>
<kwd lng="en"><![CDATA[Comprehensive Nuclear-Test-Ban Treaty (CTBT)]]></kwd>
<kwd lng="en"><![CDATA[Sound Fixing and Ranging (SOFAR) channel]]></kwd>
<kwd lng="en"><![CDATA[nuclear explo-sions]]></kwd>
<kwd lng="en"><![CDATA[Socorro Island]]></kwd>
<kwd lng="en"><![CDATA[T phases]]></kwd>
<kwd lng="en"><![CDATA[Clarión Fracture Zone]]></kwd>
<kwd lng="en"><![CDATA[Rivera Fracture Zone]]></kwd>
<kwd lng="en"><![CDATA[Pacific Ocean]]></kwd>
</kwd-group>
</article-meta>
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