Uppermost mantle seismic velocity structure beneath USArray

被引:64
作者
Buehler, J. S. [1 ]
Shearer, P. M. [1 ]
机构
[1] Univ Calif San Diego, Scripps Inst Oceanog, La Jolla, CA 92093 USA
基金
美国国家科学基金会;
关键词
Pn tomography; USArray; regional phases; seismic anisotropy; mantle lid gradient; WESTERN UNITED-STATES; REGIONAL DISTANCES; LATERAL VARIATIONS; NORTH-AMERICA; PN; ANISOTROPY; TOMOGRAPHY; LITHOSPHERE; CRUST; MODEL;
D O I
10.1002/2016JB013265
中图分类号
P3 [地球物理学]; P59 [地球化学];
学科分类号
0708 ; 070902 ;
摘要
We apply Pn tomography beneath the entire USArray footprint to image uppermost mantle velocity structure and anisotropy, as well as crustal thickness constraints, beneath the United States. The sparse source distribution in the eastern United States and the resulting longer raypaths provide new challenges and justify the inclusion of additional parameters that account for the velocity gradient in the mantle lid. At large scale, Pn velocities are higher in the eastern United States compared to the west, but we observe patches of lower velocities around the New Madrid seismic zone and below the eastern Appalachians. For much of the mantle lid below the central and eastern United States we find a moderate positive velocity gradient. In the western United States, we observe a moderate gradient in the region of the Juan de Fuca subduction zone, but no significant gradient to the south and east of this region. In terms of anisotropy, we find that the Pn fast axes generally do not agree with SKS splitting orientations, suggesting significant vertical changes in anisotropy in the upper mantle. In particular the circular pattern of the fast polarization direction of SKS in the western United States is much less pronounced in the Pn results, and in the eastern US the dominant Pn fast direction is approximately north-south, whereas the SKS fast polarizations are oriented roughly parallel to the absolute plate motion direction.
引用
收藏
页码:436 / 448
页数:13
相关论文
共 34 条
[1]   The continental lithosphere: Reconciling thermal, seismic, and petrologic data [J].
Artemieva, Irina M. .
LITHOS, 2009, 109 (1-2) :23-46
[2]   A 3-D shear velocity model of the crust and uppermost mantle beneath the United States from ambient seismic noise [J].
Bensen, G. D. ;
Ritzwoller, M. H. ;
Yang, Y. .
GEOPHYSICAL JOURNAL INTERNATIONAL, 2009, 177 (03) :1177-1196
[3]  
Blackwell D., 2011, GRC T, V35
[4]   Anisotropy and Vp/Vs in the uppermost mantle beneath the western United States fromjoint analysis of Pn and Sn phases [J].
Buehler, J. S. ;
Shearer, P. M. .
JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH, 2014, 119 (02) :1200-1219
[5]   Pn tomography of the western United States using USArray [J].
Buehler, Janine S. ;
Shearer, Peter M. .
JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH, 2010, 115
[6]   UPPER MANTLE P VELOCITY STRUCTURE OF WESTERN UNITED-STATES [J].
BURDICK, LJ ;
HELMBERGER, DV .
JOURNAL OF GEOPHYSICAL RESEARCH, 1978, 83 (NB4) :1699-1712
[7]  
Cerveny V., 1971, Theory of seismic head waves
[8]   Crust and upper mantle structure of the New Madrid Seismic Zone: Insight into intraplate earthquakes [J].
Chen, Chuanxu ;
Zhao, Dapeng ;
Wu, Shiguo .
PHYSICS OF THE EARTH AND PLANETARY INTERIORS, 2014, 230 :1-14
[9]  
Chu RS, 2013, NAT GEOSCI, V6, P963, DOI [10.1038/ngeo1949, 10.1038/NGEO1949]
[10]   Seismic structure of the crust and uppermost mantle of North America and adjacent oceanic basins: A synthesis [J].
Chulick, GS ;
Mooney, WD .
BULLETIN OF THE SEISMOLOGICAL SOCIETY OF AMERICA, 2002, 92 (06) :2478-2492