Local earthquake tomography of the Jalisco, Mexico region

Watkins, William D.; Thurber, C. H.; Abbott, Elizabeth; Brudzinski, M. R.

doi:10.1016/j.tecto.2018.01.002

Cited by 13 publications

(7 citation statements)

References 39 publications

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“…In western Mexico, where a warm oceanic slab ( T 30 km ~ 330°C) is subducting at moderate angles (~30–50°) to depth above ~100 km (Syracuse et al, 2010; Watkins et al, 2018), trench‐parallel to trench‐normal anisotropy with a short delay time of ~0.2 s for the forearc mantle was reported (Long & Wirth, 2013; Soto et al, 2009). The mantle wedge in Mexico is predicted to be extensively serpentinized (Abers et al, 2017), which may be supported by the widespread high Vp / Vs ratios above the subducting Rivera and Cocos plate interface (Watkins et al, 2018). If so, instead of the combined 2‐D corner flow and 3‐D toroidal flow model (Soto et al, 2009), the weak trench‐parallel to trench‐normal seismic anisotropy may alternatively be interpreted by the varying dip angle of serpentinized layer using our moderate‐angle subduction model (Figures 8e and 8g–8i).…”

Section: Discussionmentioning

confidence: 99%

“…This leads to weakened integrated trench‐normal and trench‐parallel seismic anisotropies at moderate‐ and high‐angle subduction zones, respectively (Figures 8e and 8f). In western Mexico, where a warm oceanic slab ( T 30 km ~ 330°C) is subducting at moderate angles (~30–50°) to depth above ~100 km (Syracuse et al, 2010; Watkins et al, 2018), trench‐parallel to trench‐normal anisotropy with a short delay time of ~0.2 s for the forearc mantle was reported (Long & Wirth, 2013; Soto et al, 2009). The mantle wedge in Mexico is predicted to be extensively serpentinized (Abers et al, 2017), which may be supported by the widespread high Vp / Vs ratios above the subducting Rivera and Cocos plate interface (Watkins et al, 2018).…”

Section: Discussionmentioning

confidence: 99%

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Geneses of Two Contrasting Antigorite Crystal Preferred Orientations and Their Implications for Seismic Anisotropy in the Forearc Mantle

et al. 2020

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Crystal preferred orientation (CPO) of antigorite is an important parameter for the interpretation of seismic anisotropies and related geodynamic processes in subduction zones. However, mechanisms for the development of various antigorite CPOs and their effects on seismic anisotropies in the forearc mantle still remain to be constrained. In this study, we investigated olivine and antigorite CPOs and calculated seismic anisotropies of the serpentinized peridotites from Val Malenco, Central Alps. The results show that antigorite in the olivine-rich (weakly serpentinized) layer displays an L-type CPO (i.e., (h0l) plane//foliation and [010] axis//lineation), whereas antigorite in the antigorite-rich (highly serpentinized) layer develops an LS-b-type CPO (i.e., (001) plane//foliation and [010] axis//lineation). The antigorite L-type CPO is most likely formed by diffusion and dislocation creep accommodated phase boundary sliding and substantial grain rotation at a higher temperature and smaller strain regime. In contrast, the development of an antigorite LS-b-type CPO requires diffusion and dislocation creep accommodated grain boundary sliding, smaller contribution of grain rotation, and significant role of dissolution-precipitation creep at a lower temperature and larger strain regime. In this context, we propose an antigorite CPO distribution model in the forearc mantle. Based on this model and under vertically incident teleseismic waves, if significant serpentinization and asymmetric shearing do indeed occur within serpentinized layers, then strong and weak trench-parallel seismic anisotropies can be expected for cold and warm moderate-angle subduction zones, respectively. This model may provide an alternative interpretation on the seismic anisotropy observations in some modern subduction systems. Plain Language Summary Antigorite is an important hydrous silicate mineral commonly present in deep subduction zone and thus contains important information concerning subduction dynamics. Previous studies have suggested that antigorite aggregates can be deformed ductilely and exhibit various types of crystal preferred orientations (CPOs)-alignments of crystallographic axes and planes along preferential directions in a structural reference frame-generally via the mechanism of dislocation creep. However, based on our natural sample study, we discovered that at least two types of antigorite CPO (i.e., L and LS-b types) can develop dominantly by the mechanisms such as grain and phase boundary sliding, grain rotation, and dissolution-precipitation creep. Combined with their hydration, temperature, and strain conditions, we conceived a model of antigorite CPO distributions in the forearc mantle at subduction zones with different thermal states and subduction angles. This model may provide an alternative interpretation on the observed strong and weak trench-parallel seismic anisotropies (i.e., fast shear wave polarizing parallel to the strike of trench) in some modern cold (e.g., Tonga, Aleutians, Izu-Bonin, and Ryukyu) and warm ...

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Geneses of Two Contrasting Antigorite Crystal Preferred Orientations and Their Implications for Seismic Anisotropy in the Forearc Mantle

et al. 2020

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“…Incorporating relative travel time in the inversion, the accuracy of the retrieved 3D velocity structure is also improved; thus, more fine structure of the underground media can be recovered. This method has become widely used recently in determining 3D velocity structure inversion in different regions (Thurber et al, 2004(Thurber et al, , 2007Okada et al, 2006Okada et al, , 2007Hofstetter et al, 2012;Allam et al, 2014;Wu HB et al, 2018;Watkins et al, 2018;Li DH et al, 2021). When matching earthquake event pairs, the maximum distance between event pairs were set to 10 km; every earthquake event was matched to more than 30 other events.…”

Section: Imaging Methodsmentioning

confidence: 99%

Upper crustal velocity and seismogenic environment of the <em>M</em>7.0 Jiuzhaigou earthquake region in Sichuan, China

Ding

Zhan

et al. 2021

Earth and Planetary Physics

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The P-wave velocity structure of the upper crust around the Jiuzhaigou earthquake region shows obvious lateral inhomogeneity, lowvelocity anomalies are observed at the intersection of shallow part of Minjiang and Tazang faults. qThe relocated earthquake sequence distributed along the NW-SE direction and ends near the intersection of the Minjiang and Tazang faults, the inhomogeneous variation of the velocity structure of the Jiuzhaigou earthquake region and its surrounding medium is the deep structural factor controlling the spatial distribution of the mainshock and its sequence. qThe crustal low-velocity layer of northeastern Songpan-Garzê Block stretches into Minshan Mountain, and migrates to the northeast, the tendency to emerge as a shallow layer is impeded by the high velocity zone of Nanping Nappe tectonics and Bikou Block.

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“…Volcán de Colima (Mexico) and the surrounding Colima Volcanic Complex were imaged using both LET (Ochoa-Chávez et al, 2016;Watkins et al, 2018;Sychev et al, 2019) and SWT (Spica et al, 2014;Escudero and Bandy, 2017;Spica et al, 2017). All these studies found evidence for low seismic velocities in the crust beneath Colima at depth of about 10 km-25 km, although depth ranges from each study differ.…”

Section: Colimamentioning

confidence: 99%

Advances in seismic imaging of magma and crystal mush

et al. 2022

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Seismic imaging methods have provided detailed three-dimensional constraints on the physical properties of magmatic systems leading to invaluable insight into the storage, differentiation and dynamics of magma. These constraints have been crucial to the development of our modern understanding of magmatic systems. However, there are still outstanding knowledge gaps resulting from the challenges inherent in seismic imaging of volcanoes. These challenges stem from the complex physics of wave propagation across highly heterogeneous low-velocity anomalies associated with magma reservoirs. Ray-based seismic imaging methods such as travel-time and surface-wave tomography lead to under-recovery of such velocity anomalies and to under-estimation of melt fractions. This review aims to help the volcanologist to fully utilize the insights gained from seismic imaging and account for the resolution limits. We summarize the advantages and limitations of the most common imaging methods and propose best practices for their implementation and the quantitative interpretation of low-velocity anomalies. We constructed and analysed a database of 277 seismic imaging studies at 78 arc, hotspot and continental rift volcanoes. Each study is accompanied by information about the seismic source, part of the wavefield used, imaging method, any detected low-velocity zones, and estimated melt fraction. Thirty nine studies attempted to estimate melt fractions at 22 different volcanoes. Only five studies have found evidence of melt storage at melt fractions above the critical porosity that separates crystal mush from mobile magma. The median reported melt fraction is 13% suggesting that magma storage is dominated by low-melt fraction crystal mush. However, due to the limits of seismic resolution, the seismological evidence does not rule out the presence of small (<10 km3) and medium-sized (<100 km3) high-melt fraction magma chambers at many of the studied volcanoes. The combination of multiple tomographic imaging methods and the wider adoption of methods that use more of the seismic wavefield than the first arriving travel-times, promise to overcome some of the limitations of seismic tomography and provide more reliable constraints on melt fractions. Wider adoption of these new methods and advances in data collection are needed to enable a revolution in imaging magma reservoirs.

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Local earthquake tomography of the Jalisco, Mexico region

Cited by 13 publications

References 39 publications

Geneses of Two Contrasting Antigorite Crystal Preferred Orientations and Their Implications for Seismic Anisotropy in the Forearc Mantle

Geneses of Two Contrasting Antigorite Crystal Preferred Orientations and Their Implications for Seismic Anisotropy in the Forearc Mantle

Upper crustal velocity and seismogenic environment of the <em>M</em>7.0 Jiuzhaigou earthquake region in Sichuan, China

Advances in seismic imaging of magma and crystal mush

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