Is the Moho flat? Seismic evidence for a rough crust-mantle interface beneath the northern Basin and Range

Larkin, Steven P.; Levander, A.; Henstock, T.; Pullammanappallil, S.

doi:10.1130/0091-7613(1997)025<0451:itmfse>2.3.co;2

Cited by 21 publications

(19 citation statements)

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“…Seismic refraction and reflection techniques have provided relatively high resolution images of the lower crust and upper mantle since the late 1970's Oliver (1982). (Hale & Thompson 1982;Larkin et al 1997;Morozov et al 2001;Balling 2000). (Hale & Thompson 1982;Larkin et al 1997;Morozov et al 2001;Balling 2000).…”

Section: Introductionmentioning

confidence: 99%

Modelling and imaging the Moho transition: the case of the southern Urals

Carbonell

Muset

Pérez-Estaún

2002

Geophysical Journal International

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Summary Synthetic seismic modelling is used to test different possible structures and forming processes of the lower crust and Moho. One and two dimensional synthetic seismic modelling of the Moho reflection is carried out to constrain the internal structure of a crust–mantle transition. A reflectivity algorithm was used to calculate the synthetic seismograms for models of the crust–mantle transition consisting of gradient zones and layered sequences. The synthetic seismograms for models consisting of laterally variable velocity structure were calculated by an explicit finite difference wave equation algorithm. The laterally heterogeneous transition models can be achieved by assuming a Moho with different degrees of variable topography or laterally discontinuous layering. The effects of a low velocity surface cover on the seismic signature of deep signals is also analysed. The seismic modelling coupled with stacked images of wide‐angle seismic reflection data constrain the case history of the Moho transition beneath the southern Urals. A smooth gradational crust–mantle transition (gradient velocity–depth function) does not predict the seismic features observed in the shot records. The coda of the PmP and the amplitude behaviour of this phase with offset are modelled with a 6 km thick transition zone which consists of approximately 600 m thick, laterally variable layers with a bimodal velocity distribution. The horizontal component stacks of the wide‐angle data feature arcuate events suggesting boudin like structures or a boundary with topographic relief. High amplitude sub‐Moho reflections support that the structural complexity of the crust–mantle transition can be followed to the upper mantle suggesting eastward dipping structures indicating, either, remnants of an old subduction zone, trapped crustal material within the mantle, or active crust–mantle interactions.

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Section: Introductionmentioning

confidence: 99%

Modelling and imaging the Moho transition: the case of the southern Urals

Carbonell

Muset

Pérez-Estaún

2002

Geophysical Journal International

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“…The composition of the material may change gradually and produce a boundary layer of gradient velocity change. For a gradient velocity boundary, the reflected seismic wave has small amplitude at near offset and large amplitude at far offset (Larkin et al, 1997). The new seismic profile verified such a pattern of amplitude variation as shown in Fig.…”

Section: Verification and Interpretation Of The Upper Mantle Reflectormentioning

confidence: 51%

Crustal and upper-mantle seismic reflectors beneath the Three Gorges Reservoir region

Zou

Zhou

Liao³

2011

J. Earth Sci.

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Seismic studies of the crustal structure beneath the Three Gorges Reservoir (TGR) region in Central China have been limited by the sparse and uneven distribution of seismic stations. To increase the station coverage, we made three deployments of a mobile seismologic array in the TGR region during the three summers from 2008 to 2010. Here we present interpretations along a west-east profile through the central TGR region based on new seismic waveform data and a velocity model constrained by regional earthquake data. Two strong mid-crustal reflection interfaces at depths around 10 and 20 km are seen under the TGR. The shallow reflector defines the bottom of the Zigui (秭归) basin. The new waveform data show that the amplitude of the Moho reflection is quite weak, and beneath theMoho, there is a strong reflector around 54-km depth. It is likely that in the TGR region, the Moho is a gradient rather than a sharp boundary. We speculate that the gradient Moho and the 54-km-deep reflector in the upper mantle in the TGR region may be by-products of the Qinling (秦岭)-Dabie (大别) orogen.

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“…Mega-waves, although a rare phenomenon (White and Fornberg, 1998), harness great energy for a limited time. They are the indirect result of chaotic system behaviour in the outer core inevitably forcing wave motion along sharp chemical composition discontinuities such as the Earth's core-mantle (Gutenberg) and crust-mantle (Moho) boundaries (Larkin et al, 1997;d'Acremont et al, 2002) in sequence away from equilibrium, allowing the formation of random nonlinear mega-waves.…”

Section: Topography Of the Core And Extreme Amplitude Wavesmentioning

confidence: 98%