<p>Many earthquakes in global moment tensor catalogs contain non-double-couple (NDC) components, but it is often unclear whether they reflect source complexity or artifacts of the inversion. Global moment tensor catalogs constrain the isotropic component during the inversion and thus report deviatoric solutions. Therefore, this study analyzes the reported compensated linear vector dipole (CLVD) components in global catalogs. I test whether intraplate earthquakes with centroid depths of 60 km or less have larger NDC components than other earthquakes using the Global Centroid Moment Tensor (GCMT) catalog and the CMT3D catalog. In the GCMT catalog, 663 intraplate earthquakes have a mean <InlineEquation ID="IEq1"> <EquationSource Format="TEX">$|2\varepsilon |$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mo stretchy="false">|</mo> <mn>2</mn> <mi>ε</mi> <mo stretchy="false">|</mo> </mrow> </math></EquationSource> </InlineEquation> of 26.35%, higher than the mean of the entire GCMT catalog, 23.51%, and higher than the mean of 54658 non-intraplate earthquakes, 23.49%. The difference between intraplate and non-intraplate earthquakes is 2.86 percentage points and is statistically significant (<InlineEquation ID="IEq2"> <EquationSource Format="TEX">$p=2.0\times 10^{-4}$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>p</mi> <mo>=</mo> <mn>2.0</mn> <mo>×</mo> <msup> <mn>10</mn> <mrow> <mo>-</mo> <mn>4</mn> </mrow> </msup> </mrow> </math></EquationSource> </InlineEquation>). The difference remains when continental and oceanic domains are analyzed separately, when different depth and distance thresholds are used, after excluding earthquakes near active volcanoes, and after accounting for differences in magnitude, centroid depth, mechanism, and geologic environment. Comparing the distributions of NDC components, I find that the difference in mean NDC components is not caused by a few events with very large NDC components, but reflects a broader shift toward larger <InlineEquation ID="IEq3"> <EquationSource Format="TEX">$|2\varepsilon |$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mo stretchy="false">|</mo> <mn>2</mn> <mi>ε</mi> <mo stretchy="false">|</mo> </mrow> </math></EquationSource> </InlineEquation>. Earthquakes that appear in both the GCMT and CMT3D catalogs also show larger NDC components for intraplate events than for non-intraplate events, indicating that the difference is not specific to one catalog. The effect is small in absolute magnitude, but it is detected repeatedly when intraplate earthquakes are compared with non-intraplate earthquakes in global moment tensor catalogs. It is therefore consistent with greater source complexity of intraplate earthquakes, possibly due to rupture on immature or unfavorably oriented faults and to heterogeneous stress fields. However, the difference may also include artifacts of the moment tensor inversion caused by Earth-model uncertainty in intraplate regions. These results show that moment tensor inversions of intraplate earthquakes are expected to yield larger NDC components, which may reflect greater source complexity, inversion-related artifacts, or both.</p>

Non-double-couple components of intraplate earthquakes

期刊论文
发表日期：

2026年7月23日

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Boris Rösler

摘要

Many earthquakes in global moment tensor catalogs contain non-double-couple (NDC) components, but it is often unclear whether they reflect source complexity or artifacts of the inversion. Global moment tensor catalogs constrain the isotropic component during the inversion and thus report deviatoric solutions. Therefore, this study analyzes the reported compensated linear vector dipole (CLVD) components in global catalogs. I test whether intraplate earthquakes with centroid depths of 60 km or less have larger NDC components than other earthquakes using the Global Centroid Moment Tensor (GCMT) catalog and the CMT3D catalog. In the GCMT catalog, 663 intraplate earthquakes have a mean $|2\varepsilon |$ $| 2 ε |$ of 26.35%, higher than the mean of the entire GCMT catalog, 23.51%, and higher than the mean of 54658 non-intraplate earthquakes, 23.49%. The difference between intraplate and non-intraplate earthquakes is 2.86 percentage points and is statistically significant ( $p=2.0\times 10^{-4}$ $p = 2.0 \times 10^{- 4}$ ). The difference remains when continental and oceanic domains are analyzed separately, when different depth and distance thresholds are used, after excluding earthquakes near active volcanoes, and after accounting for differences in magnitude, centroid depth, mechanism, and geologic environment. Comparing the distributions of NDC components, I find that the difference in mean NDC components is not caused by a few events with very large NDC components, but reflects a broader shift toward larger $|2\varepsilon |$ $| 2 ε |$ . Earthquakes that appear in both the GCMT and CMT3D catalogs also show larger NDC components for intraplate events than for non-intraplate events, indicating that the difference is not specific to one catalog. The effect is small in absolute magnitude, but it is detected repeatedly when intraplate earthquakes are compared with non-intraplate earthquakes in global moment tensor catalogs. It is therefore consistent with greater source complexity of intraplate earthquakes, possibly due to rupture on immature or unfavorably oriented faults and to heterogeneous stress fields. However, the difference may also include artifacts of the moment tensor inversion caused by Earth-model uncertainty in intraplate regions. These results show that moment tensor inversions of intraplate earthquakes are expected to yield larger NDC components, which may reflect greater source complexity, inversion-related artifacts, or both.