<?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>S0016-71692017000100007</article-id>
<article-id pub-id-type="doi">10.19155/geofint.2017.056.1.1</article-id>
<title-group>
<article-title xml:lang="en"><![CDATA[Unusual, equivocal Rayleigh-dispersion curves for simple models taking into account the special propagation conditions in the valley of Mexico City (CDMX) - Preliminary results]]></article-title>
</title-group>
<contrib-group>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Malischewsky]]></surname>
<given-names><![CDATA[Peter G.]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Forbriger]]></surname>
<given-names><![CDATA[Thomas]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Lomnitz]]></surname>
<given-names><![CDATA[Cinna]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
</contrib-group>
<aff id="A01">
<institution><![CDATA[,University Jena Institute of Geosciences Friedrich-Schiller ]]></institution>
<addr-line><![CDATA[ ]]></addr-line>
<country>Germany</country>
</aff>
<aff id="A02">
<institution><![CDATA[,Karlsruhe Institute of Technology  ]]></institution>
<addr-line><![CDATA[Karlsruhe ]]></addr-line>
<country>Germany</country>
</aff>
<aff id="A03">
<institution><![CDATA[,Universidad Nacional Autonoma de México Instituto de Geofísica ]]></institution>
<addr-line><![CDATA[ CDMX]]></addr-line>
<country>Mexico</country>
</aff>
<pub-date pub-type="pub">
<day>00</day>
<month>03</month>
<year>2017</year>
</pub-date>
<pub-date pub-type="epub">
<day>00</day>
<month>03</month>
<year>2017</year>
</pub-date>
<volume>56</volume>
<numero>1</numero>
<fpage>7</fpage>
<lpage>12</lpage>
<copyright-statement/>
<copyright-year/>
<self-uri xlink:href="http://www.scielo.org.mx/scielo.php?script=sci_arttext&amp;pid=S0016-71692017000100007&amp;lng=en&amp;nrm=iso"></self-uri><self-uri xlink:href="http://www.scielo.org.mx/scielo.php?script=sci_abstract&amp;pid=S0016-71692017000100007&amp;lng=en&amp;nrm=iso"></self-uri><self-uri xlink:href="http://www.scielo.org.mx/scielo.php?script=sci_pdf&amp;pid=S0016-71692017000100007&amp;lng=en&amp;nrm=iso"></self-uri><abstract abstract-type="short" xml:lang="en"><p><![CDATA[Abstract: Other than commonly assumed in seismology, the phase velocity of Rayleigh waves not necessarily is a single-valued function of frequency. We demonstrate this for the first higher mode in simple models of a homogeneous layer on top of a homogeneous halfspace (LOH), which are used for the subsurface of the Texcoco zone in Mexico City valley in previous studies. In the structure of a homegenous layer with fixed bottom (LFB) the phenomenon exists for values of Poisson&#8217;s ratio between 0.19 and 0.5 and is most pronounced for P-velocity being three times S-velocity (Poisson&#8217;s ratio of 0.4375). This type of dispersion is demonstrated and a discussion of their possible fatal consequences for methods customarily used in seismology for dispersion analysis and synthesis of dispersion relations is presented.]]></p></abstract>
<abstract abstract-type="short" xml:lang="es"><p><![CDATA[Resumen: Contrario a lo que normalmente es asumido en sismologia, la fase-velocidad de olas Rayleigh no necesariamente es una función de valor único de frecuencia. Se demuestra esto para el primer modo más alto en modelos simples de una capa homogénea encima de un semiespacio homogéneo (LOH), los cuales, han sido utilizados en estudios anteriores en el subsuelo de la zona de Texcoco en el valle de Ciudad de México. En la estructura de una capa homogénea con fondo fijo (LFB) el fenómeno existe para valores del coeficiente de Poisson entre 0.19 y 0.5 y es más pronunciado para velocidades de P que son tres veces la velocidad de S (Coeficiente de Poisson de 0.4375). En este trabajo se demuestra este tipo de dispersión y se discuten sus posibles consecuencias fatales para los métodos habitualmente usados en sismología en el análisis de dispersión y síntesis de relaciones de dispersión.]]></p></abstract>
<kwd-group>
<kwd lng="es"><![CDATA[Ondas de Rayleigh]]></kwd>
<kwd lng="es"><![CDATA[dispersión]]></kwd>
<kwd lng="es"><![CDATA[ambigüedad]]></kwd>
<kwd lng="es"><![CDATA[valle de CDMX]]></kwd>
<kwd lng="en"><![CDATA[Rayleigh waves]]></kwd>
<kwd lng="en"><![CDATA[dispersion]]></kwd>
<kwd lng="en"><![CDATA[ambiguity]]></kwd>
<kwd lng="en"><![CDATA[Mexico City valley]]></kwd>
</kwd-group>
</article-meta>
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