GeodVel: it's the better geodetic Plate Tectonic model at the border between NorthAmerica and Pacific?

Jose Javier Gonzàlez-Garcìa, Alejandro Gonzalez-Ortega, Juan Carlos Robles-Avalos, & Hebert Martinez-Barcena

Published August 15, 2019, SCEC Contribution #9729, 2019 SCEC Annual Meeting Poster #214

We use the Euler vector parameters and Google Earth as visualization tool looking for the key geomorphology features along the Pacific-NorthAmerican plates border (Pa-Na) at Las California's and beyond, following the original Triple Junction (TJ) travel to the NW and SE. Our premise is that Pa-Na Euler vector is constant since the first contact between NorhAmerica (NA) and Pacific (PA) plates.

Using simple geometric approach, first contact position of NA and PA have 45.0° azimuth (heading) with respect to Pa-Na rotation pole (ECEF, geodetic coordinates). After several model’s comparison, including ours; we prefer GeodVel (Lat. 50.54°, Lon. -75.07° and 0.777°/Ma), due to ~30 Ma origin time for NA and PA first contact at Las Californias's region as suggested by most geological studies.

In the NW side, the colatitude (35.71°) of Mendocino Triple Junction (MTJ) is obtained considering the ground length between a site near Point Reyes and NaPa pole, resulting in a position with Lat. 40.40° and Lon. -124.92°. The heading of MTJ to Pa-Na pole is 56.44°; then, the origin time given by {[(56.44°- 45.0°) x 2] / 0.777°/Ma} is 29.45 Ma. For the SE side, we considered the Tamayo Fracture Zone (TFZ) as the main limit between NA and PA with 37.66° colatitude at the NA/PA/RIVERA TJ, however, its heading does not correspond to our premise of a constant Pa-Na Euler vector; then, we defined it as a Virtual southeast TJ (VsTJ, with 37.66° colatitude and 33.56° heading (Lat. 22.34°, Lon. -107.25°) just NW of Islas Tres Marias where MesoAmerican Trench begins.

Following the colatitude of TFZ, the VsTJ will be, in 10.1 Ma, at 20.2°, -103.5° on the northernmost site of a future spreading center between Jalisco Block and mainland Mexico. After 33.1 Ma from now VsTJ would be at the Cocos/NA/Caribe TJ (15.2°, -95.6° or 38.9° colatitude and 20.7° heading); at the same time MTJ would be at the present location of PA/NA/Juan de Fuca TJ (51.6°, -130.8°) with 34.24° colatitude, same as that of Salton Buttes, southernmost location of the San Andreas Fault. Highest velocity for Geodvel is located at: Okhotsk (NA?)/Eurasia?/Philippine Sea TJ (34.5°, 138.7°) with heading equal to that of CO/NA/CA TJ; and -39.9°, -75.1° (90° colatitude, 0° heading) near SouthAmerica/Antartica/Nazca TJ: source regions of the larger Japan (2011) and Chlle (1960) earthquakes, respectively.

Gonzàlez-Garcìa, J., Gonzalez-Ortega, A., Robles-Avalos, J., & Martinez-Barcena, H. (2019, 08). GeodVel: it's the better geodetic Plate Tectonic model at the border between NorthAmerica and Pacific?. Poster Presentation at 2019 SCEC Annual Meeting.

Related Projects & Working Groups
Tectonic Geodesy