Wave fields and crustal structure of the northeastern basin of the PacificOcean in the Murray Fracture Zone region from the data of seismic studies

The results of detailed seismic studies with the deep seismic sounding meth od using an array of bottom seismographs and powerful air guns performed in the Murray Fracture Zone region are presented. On the northern side of the fault (with an age of about 46 Ma), an area-covering experiment on the ses mic tomography of the earth's crust was implemented, while on the southern one (with an age of about 30 Ma), a sublatitudinal deep seismic sounding pr ofile was observed. In the first arrivals of the bottom seismograph records , refracted waves related to the principal layers of the earth's crust (2B, 2C, and 3) and upper mantle (M) were recognized. In the subsequent arrival s, waves reflected from the Mohorovicic discontinuity and converted PSP wav es corresponding to layers 2, 3, and M were recorded. Using two-dimensional modeling, seismic models and cross sections were compiled. Layers 213, 2C, 3, and the upper mantle are characterized by the compressional wave veloci ty values of 5.1-5.4, 5.8-6.1, 6.6-7.0, and 8.2 km/s and vertical velocity gradients of 0.4, 0.3, 0.1, and 0.06 l/s, respectively. The shear wave velo city in layers 2, 3, and M are respectively equal to 3.2-3.3, 3.7-3.8, and 4.2-4.3 km/s. The thickness of the earth's crust on the northern side of th e fracture zone equals 7-8 km, while on its southern side it is 4-5 km.