Transcript Upper Mantle of the GoC Region: Results from the NARS-Baja Array
Upper Mantle of the GoC Region: Results from the NARS-Baja Array
Raúl Castro (CICESE) Robert Clayton (CALTECH) Francesca Di Luccio (INGV) Mathias Obrebski (CICESE) Raul Valenzuela (IGEOF-UNAM) Xiaomei Zhang (Utrecht University)
New Array Monitors Seismic Activity near the Gulf of California in Mexico
J. Trampert, H. Paulssen, A. van Wettum ,
Utrecht University
J. Ritsema, R. Clayton,
California Institute of Technology
R. Castro, C. Rebollar, A. Perez-Vertti,
CICESE
Eos, Vol. 84, No. 4 28 January 2003
Equipment at stations of NARS-Baja array. STS2 sensors, data logger, GPS receiver, laptop for data acquisition and timing.
RESNOM Seismic Network (CICESE)
A. Vidal, L. Munguía, F. Farfan, I. Mendez, L. Orozco, O.Galvez
RESNES Seismic Network (UNAM - CICESE)
R. Castro, C. Jacques, O. Romero, L. Inzunza
NARS-Baja, RESBAN, RESNOM, RESNES
A Study of Seismic Anisotropy in Northern Baja California, Mexico, using SKS Waves
M. Obrebski 1 , R. Castro 1 , and C. Rebollar 1 S., van Benthem 2,3 , (Utrecht University) R.W. Valenzuela 2 , (IGEOF-UNAM) (CICESE)
A Study of Seismic Anisotropy in Northern Baja California, Mexico, using SKS Waves
Obrebski, Castro, van Benthem, Valenzuela and Rebollar
A Study of Seismic Anisotropy in Northern Baja California, Mexico, using SKS Waves
Obrebski, Castro, van Benthem, Valenzuela and Rebollar
RESULTS
Obrebski, M., Castro, R.R., Valenzuela, R.W., van Benthem, S. and Rebollar, C. (2006).
Shear-wave splitting observations at the regions of northern Baja California and southern Basin and Range in Mexico,
GRL (accepted).
A Study of Seismic Anisotropy in Northern Baja California, Mexico, using SKS Waves
Obrebski, Castro, van Benthem, Valenzuela and Rebollar
North Baja Transect (NBT)
Lewis, J.L., S.M. Day, H. Magistrale, R. Castro, L. Astiz, C. Rebollar, J. Eakins, F. Vernon and J.N. Brune (2001). Crustal thickness of the peninsular ranges and gulf extensional province in the Californias,
Jour. of Geophys. Res.,
106, 13,599-13,611.
A Study of Seismic Anisotropy in Northern Baja California, Mexico, using SKS Waves
Obrebski, Castro, van Benthem, Valenzuela and Rebollar
Results using NBT data set
Upper Mantle Shear Wave Anisotropy Under Stations around the Southern Gulf of California
S., van Benthem, (Utrecht University - UNAM) R.W. Valenzuela, (IGEOF-UNAM) M. Obrebski, and R.R. Castro, (CICESE)
Upper mantle shear wave anisotropy around the southern Gulf of California Individual measurements
Upper Mantle Shear Wave Anisotropy Under Stations around the Southern Gulf of California
v an Benthem, Valenzuela, Obrebski, and Castro
Upper mantle shear wave anisotropy around the southern Gulf of California Averaged measurements
The upper mantle beneath Gulf of California: a surface waves study
Xiaomei Zhang & Sergei Lebedev & Hanneke Paulssen Utrecht University (The Netherlands)
Methods
two station method
the automated multimode inversion (AMI)
The upper mantle beneath Gulf of California: a surface waves study
Zhang, Lebedev, and Paulssen
Two Station Method (T.Meier et al., 2004)
The upper mantle beneath Gulf of California: a surface waves study
Zhang, Lebedev, and Paulssen
1-D S-velocity models determined for the station combinations
The 1-D shear wave velocity inversions station pair NE73-NE80 (at the northern part of the Gulf) station pair NE70-NE79 (along the peninsula) station pair NE79-NE83 (at the mouth of the Gulf) station pair NE80-NE83 (along the continent)
The automated multimode inversion (AMI) (S. Lebedev et al., 2004) Figure shows all ray paths (512) of our data set. Most ray paths are along the Gulf either from the north or from the south. One example by automated multimode inversion
The upper mantle beneath Gulf of California: a surface waves study
Zhang, Lebedev, and Paulssen
Summary of first results
From north to south toward the mouth of the Gulf:
1) The crust thickness inside the Gulf decreases; 2) The thickness of the low velocity zone in the upper 200 km increases.
Along the peninsula and along the continent:
1) The crust thickness is continental; 2) The low velocity zone in the upper 200 km is thinner than inside the Gulf.
Velocity Model for the Gulf of California
R.W. Clayton, P. Persaud (California Institute of Technology) F. Di Luccio (Istituto Nazionale di Geofisica e Vulcanologia) X. Perez-Campos (IGEOF-UNAM)
• Model based on surface wave group velocities and • receiver functions.
The surface wave group velocities are determined from earthquakes located in the Gulf and from correlations of seismic noise.
• 1.
Main features of model: mid-Gulf high-velocity zone 2. 50% thinning of the crust on eastern side of Peninsula • Future work: construct a model for the region that can be used as a framework for detailed studies.