{"title":"Constraining Earth's mantle rheology with Love and Shida numbers at the M2 tidal frequency","authors":"Dargilan Oliveira Amorim , Tamara Gudkova","doi":"10.1016/j.pepi.2024.107144","DOIUrl":null,"url":null,"abstract":"<div><p>We use measurements of Earth's tidal response at the <span><math><msub><mi>M</mi><mn>2</mn></msub></math></span><span> frequency to constrain the rheology of its mantle. The viscoelasticity<span> and anelasticity of the planet are modeled with an Andrade rheology that depends on two parameters: </span></span><span><math><mi>α</mi></math></span> and <span><math><mi>ζ</mi></math></span>. In this paper, we propose an improved algorithm to compute Earth's tidal deformation. Its Love and Shida numbers <span><math><msub><mi>k</mi><mn>2</mn></msub></math></span>, <span><math><msub><mi>h</mi><mn>2</mn></msub></math></span>, <span><math><msub><mi>k</mi><mn>3</mn></msub></math></span> and <span><math><msub><mi>l</mi><mn>2</mn></msub></math></span> as well as the tidal lag <span><math><mi>ϵ</mi></math></span> were calculated for two viscosity profiles and for a wide range of values of <span><math><mi>α</mi></math></span> and <span><math><mi>ζ</mi></math></span>. By comparing our results with geodetic measurements we obtain the range of values of <span><math><mi>α</mi></math></span> and <span><math><mi>ζ</mi></math></span> that successfully describes Earth's viscoelastic behavior. Values of <span><math><mi>ζ</mi></math></span> as high as <span><math><msup><mn>10</mn><mn>5</mn></msup></math></span> can not be excluded. For <span><math><mi>ζ</mi><mo>=</mo><mn>1</mn></math></span>, <span><math><mi>α</mi></math></span> should be in the range from 0.19 to 0.33, while for a <span><math><mi>ζ</mi><mo>=</mo><msup><mn>10</mn><mn>5</mn></msup></math></span>, <span><math><mi>α</mi></math></span><span> is most likely between 0.11 and 0.17. We believe that a similar rheology should be used in geophysical models of other rocky planets and satellites. The obtained results are mostly representative of the lower mantle.</span></p><p>We have also shown that for several combinations of the two parameters <span><math><mi>α</mi></math></span> and <span><math><mi>ζ</mi></math></span> we could obtain nearly identical values of Earth's <span><math><mi>ℜ</mi><mfenced><msub><mi>k</mi><mn>2</mn></msub></mfenced></math></span>, <span><math><mi>ℜ</mi><mfenced><msub><mi>h</mi><mn>2</mn></msub></mfenced></math></span>, <span><math><mi>ℜ</mi><mfenced><msub><mi>l</mi><mn>2</mn></msub></mfenced></math></span> and <span><math><mi>ℜ</mi><mfenced><msub><mi>k</mi><mn>3</mn></msub></mfenced></math></span> with considerably different values of the associated tidal lag. This shows that the approach of always setting <span><math><mi>ζ</mi><mo>=</mo><mn>1</mn></math></span> might be too simplistic and an Andrade rheology with two free parameters is needed to constrain both the real and imaginary parts of Love and Shida numbers.</p></div>","PeriodicalId":54614,"journal":{"name":"Physics of the Earth and Planetary Interiors","volume":"347 ","pages":"Article 107144"},"PeriodicalIF":2.4000,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Physics of the Earth and Planetary Interiors","FirstCategoryId":"89","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0031920124000025","RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"GEOCHEMISTRY & GEOPHYSICS","Score":null,"Total":0}
引用次数: 0
Abstract
We use measurements of Earth's tidal response at the frequency to constrain the rheology of its mantle. The viscoelasticity and anelasticity of the planet are modeled with an Andrade rheology that depends on two parameters: and . In this paper, we propose an improved algorithm to compute Earth's tidal deformation. Its Love and Shida numbers , , and as well as the tidal lag were calculated for two viscosity profiles and for a wide range of values of and . By comparing our results with geodetic measurements we obtain the range of values of and that successfully describes Earth's viscoelastic behavior. Values of as high as can not be excluded. For , should be in the range from 0.19 to 0.33, while for a , is most likely between 0.11 and 0.17. We believe that a similar rheology should be used in geophysical models of other rocky planets and satellites. The obtained results are mostly representative of the lower mantle.
We have also shown that for several combinations of the two parameters and we could obtain nearly identical values of Earth's , , and with considerably different values of the associated tidal lag. This shows that the approach of always setting might be too simplistic and an Andrade rheology with two free parameters is needed to constrain both the real and imaginary parts of Love and Shida numbers.
期刊介绍:
Launched in 1968 to fill the need for an international journal in the field of planetary physics, geodesy and geophysics, Physics of the Earth and Planetary Interiors has now grown to become important reading matter for all geophysicists. It is the only journal to be entirely devoted to the physical and chemical processes of planetary interiors.
Original research papers, review articles, short communications and book reviews are all published on a regular basis; and from time to time special issues of the journal are devoted to the publication of the proceedings of symposia and congresses which the editors feel will be of particular interest to the reader.