Minimum travel time tree algorithm for seismic ray tracing: improvement in efficiency

Zhao, Aiwu; Zhang, Zhongjie; Teng, Jun

doi:10.1088/1742-2132/1/4/001

Cited by 50 publications

(28 citation statements)

References 9 publications

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“…A preliminary indication of the results from the Pg phases is that the shallow covering layer along the profile is not too thick and the velocity is up to 4.0 km/s. Based on the picked first-arrival Pg phases from the six shots, the velocity structure of the upper crust is inverted by the finite difference method (Vidale, 1988;Hole, 1992;Zhao et al, 2004;Zhang, 2013a, 2013b;Lan et al, 2012aLan et al, , 2012bLiu et al, 2012;Zhao et al, 2014;Ma and Zhang, 2014). The velocity structure of the upper crust so determined can be considered as the initial model of the shallow crust that is used to then invert the crustal velocity structure (Xu et al, 2014a).…”

Section: First Arrivalsmentioning

confidence: 99%

Crustal velocity structure in the Emeishan large igneous province and evidence of the Permian mantle plume activity

Zhang

Liu

et al. 2015

Sci. China Earth Sci.

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The Emeishan large igneous province (ELIP) in SW China is interpreted to be associated with an ancient mantle plume. Most of the constraints on the role of mantle plume in the generation of the Emeishan flood basalts were provided by geological and geochemical methods, but the geophysical investigation is very limited. In order to better understand the deep structure and features of ELIP, we have studied the crustal velocity structure using the data acquired from the Lijiang-Panzhihua-Qingzhen wide-angle seismic profile. This profile crosses the three sub-zones of the ELIP (the inner, intermediate, and outer zones), divided based on the differential erosion and uplift of the Maokou limestone. The results provided by the active source seismic experiment demonstrate: (1) The average depth of the crystalline basement along the profile is about 2 km. (2) The middle crust in the Inner Zone is characterized by high-velocity anomalies, with the average velocity of 6.26.6 km/s, which is about 0.1-0.2 km/s higher than the normal one. The velocity of the lower crust in the inner zone is 6.97.2 km/s, higher than those observed in the intermediate and outer zones (6.77.0 km/s). Relatively low velocity anomalies appear in the upper, middle and lower crusts near the junction of the inner zone and intermediate zone, probably due to the effect of the Xiaojiang fault (XJF). (3) The average velocity of the crust is comparatively low on both sides of XJF, especially on the east side, and the average velocity of the consolidated continental crust is also low there. This may suggest that the XJF extends at least down to 40 km deep, even beyond through the crust. (4) The depth to the Moho discontinuity decrease gradually from 4753 km in the inner zone, via 4250 km in the intermediate zone to 3842 km in the outer zone. In the inner zone, the Moho uplifts locally and the (consolidated) crust is characterized by high-velocity anomalies, which are likely related to intensive magma intrusion and underplating associated with melting of plume head. Overall the crustal velocity structure in the study area recorded the imprint left by the Permian Emeishan mantle plume. Emeishan large igneous province, Permian mantle plume, wide-angle seismic reflection/refraction data, Lijiang-PanzhihuaQingzhen profile, crustal velocity Citation:Xu T, Zhang Z J, Liu B F, et al. 2015. Crustal velocity structure in the Emeishan large igneous province and evidence of the Permian mantle plume activity. Science China: Earth Sciences,

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Section: First Arrivalsmentioning

confidence: 99%

Crustal velocity structure in the Emeishan large igneous province and evidence of the Permian mantle plume activity

Zhang

Liu

et al. 2015

Sci. China Earth Sci.

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“…Errors associated with travel times calculated with the minimum travel time tree algorithm are mainly dependent upon the size of model elements and the number of propagation directions of secondary waves, as shown by Moser et al [10,21] . They can be reduced further only when the size of model elements becomes smaller and the number of the propagation directions becomes larger, at the cost of more CPU time.…”

Section: Improved Algorithm For First-break Wavesmentioning

confidence: 99%

Double-Grid Algorithm for Calculating Travel Times of Wide-Angle Reflection Waves

Zhao¹,

Ding²

2005

Chinese J. Geophys.

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Layered and blocked homogeneous models are usually used in interpreting wide‐angle reflection data to forward model travel times and ray paths of wide‐angle reflection waves when we research crust structure by deep seismic exploration. In order to make the model approach the Earth, the size of the model has to be large. On the other hand, for obtaining accurate travel times and rays calculated with minimum travel time tree algorithm, the model elements have to be small, and thus the efficiency of calculation is decreased. In this paper, a double‐grid scheme is employed in calculation of travel times and ray paths in order to fast and reliably interpret deep sounding data. In the double‐grid algorithm, the model is covered with sparse and dense grids. Nodes in the sparse gird are calculated in the same way as in the single‐grid algorithm; as for the ones in the dense gird, they are done only if they are in the neighborhoods of source and geophone nodes, and the ones where velocity gradients are not zero, and the propagation areas of secondary waves are larger for interface boundary nodes than for the ones within homogenous media. The numerical example shows that the double‐grid algorithm has much higher calculation efficiency than the single‐gird one under the same accuracy condition for large layered and blocked homogenous models.

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“…Other authors proposed raytracing methods with a triangular mesh, which can be used to represent complex geological structures, but it still has the multi-path problem (Bai et al 2012). In addition, the minimum traveltime tree algorithm (MTTT) was proposed by Nakanishi and Yamaguchi (1986), and was developed by Zhao et al (2004). However, MTTT needs a larger computation cost compared to the finite-difference method, which will be used in our study.…”

Section: Introductionmentioning

confidence: 99%

Accurate Microseismic Event Location Inversion Using a Gradient-Based Method

Chen

Han

et al. 2012

All Days

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From the microseismic data collected during multi-stage hydraulic fracturing, we may pick out the first arrival times for both P-and S-waves for each event and at each geophone. With triaxial geophones, the azimuths of the events may be derived from the hodograms. The P-and S-wave arrival times contain the distance information from the event location to the geophones as well as the event initiating time. The azimuth from hodograms gives the orientation information of the event locations. Inverting these interpreted microseismic data yields the event location parameters, which can be used to characterize the hydraulic fractures for reservoir modeling. This paper presents an efficient gradient-based microseismic event location inversion method. The forward model that is used to calculate the first arrival times is the finite-difference solution of the Eikonal equation. A novel method is devised to obtain the gradient of the first arrival times to the event location parameters in addition to the first arrival times in one forward model run. The method is applied to a realistic multilayer shale gas reservoir with a horizontal well and several stages of hydraulic fractures. The results show that the first arrival times obtained from the surface geophones yield better event location parameter estimation assuming we can pick up the events from the surface geophone signal. When the geophones are placed downhole in nearby wells, the inverted event locations are less accurate than the ones with surface geophones but can have a relative good characterization fo the fracture propagation.

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Minimum travel time tree algorithm for seismic ray tracing: improvement in efficiency

Cited by 50 publications

References 9 publications

Crustal velocity structure in the Emeishan large igneous province and evidence of the Permian mantle plume activity

Crustal velocity structure in the Emeishan large igneous province and evidence of the Permian mantle plume activity

Double-Grid Algorithm for Calculating Travel Times of Wide-Angle Reflection Waves

Accurate Microseismic Event Location Inversion Using a Gradient-Based Method

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