wesnousky

The mechanical nature of plate boundary deformation is not to be elucidated solely by measures of strain accumulation.

The structure, physiography, and the spatial and temporal pattern of earthquakes are a manifestation of how that strain is released.

The relationship of strain accumulation to strain release.

Thatcher, W., G.R. Foulger, J.B. R., J. Svarc, E. Quilty, and G.W. Bawden, Present-Day deformation across the Basin and Range province, western United States, SCIENCE, 283, 1714-1718, 1999.

Bennett, R.A., B.P. Wernicke, N.A. Niemi, A.M. Friederich, and J.L. Davis, Contemporary strain rates in the northern Basin and Range province from GPS data, Tectonics, 22 (0278-7407/03/2001TC001355), 3-1 - 3-31, 2003.

What characteristics of deformation are universal to both the Walker Lane and San Andreas?Which are not?

Does the ‘Central Nevada Seismic Belt’ continue northward beyond what we observe in the historical record?

How unique or characteristic to Basin and Range deformation is the spatial and temporal clustering of earthquakes observed historically in the Central Nevada Seismic Belt?

What is the relationship of coseismic slip at a site to the recurrence time between earthquakes? Do slip characteristics repeat.?

Some Questions that arose:

Are the patterns of contemporary seismicity and strain accumulation reflected in the record of fault displacements during the latest Quaternary?

How 'rigid' is the interior Great Basin?

Where and how is strain accumulation accommodated in the Walker Lane?

Some Questions that arise:

Are the patterns of contemporary seismicity and strain accumulation reflected in the record of fault displacements during the latest Quaternary?

How 'rigid' is the central Great Basin?

Where and how is strain accumulation accommodated in the Walker Lane?

What characteristics of deformation are universal to both the Walker Lane and San Andreas?Which are not?

Does the ‘Central Nevada Seismic Belt’ continue northward beyond what we observe in the historical record?

How unique or characteristic to Basin and Range deformation is the spatial and temporal clustering of earthquakes observed historically in the Central Nevada Seismic Belt?

What is the relationship of coseismic slip at a site to the recurrence time between earthquakes? Do slip characteristics repeat.?

Walker Lane fault system

San Andreas fault system

Greater cumulative slip and a component of compression along the San Andreas system leads to a simpler pattern of active faulting than observed along the transtensional Walker Lane system

Vertical axis ‘block’ rotations shared by SA and Walker Lane systems

Central Walker Lane appears at younger stage of evolution than Southern California

Southern San Andreas SystemCentral Walker Lane

Which is stronger? What is driving force?

Decoupling of crust and upper mantle?

Distribution and rate of late Pleistocene surface rupture occurrence is in general accord with GPS measurements.

The Central Nevada Seismic Belt has been more active than the interior of the Great Basin to the north and east during the last ~20 ka.

While the historical alignment of surface ruptures that defines the Central Nevada seismic belt remains unique, the likelihood of the cluster at its observed location is greater than would be expected to the east or northward in the interior of the Great Basin.

The Central Nevada Seismic Belt does not appear to continue northward beyond its present extent.

The Central Nevada Seismic Belt may be viewed as a reentrant of relatively high strain into the slower-deforming interior of the Central Great Basin.

i.

ii.

iii.

40°

as compared to the Central Nevada Seismic Belt

0.59 to 1.37 mm/yr

and how ‘rigid’ is the interior?

17.6 m / 45 ka = 0.39 mm/yr

11.3 m / 20ka = 0.57 mm/yr

Rates equivalent to 1.0-1.4 nstr yr-1 over 400 km width

Table 3.

Fault(V) VerticalSeparation

(m)

Extension (H)=V/tan(60°)

(m)Strike$

East-WestExtension@

(HEW) (m)post 45 ka

8. Humboldt 2.7 1.6 180° 1.613. Shoshone 4.7 (penultimate) 2.7 210° 2.415. Dry Hills 1.5 (triultimate) 0.9 220° 0.718. Pequops 2.9 1.7 0° 1.7

post 20 ka6. Shawave 3.3 1.9 30° 1.77. Brady – HotSpring 2.0 1.2 195° 1.18. Humboldt 2 (recent) 1.2 180° 1.29. Santa Rosa 1-2+ 190°

10. Stillwater 2.6* 1.5 200° 1.411. Sonoma 2.4 1.4 150° 1.213. Shoshone 0.4 (recent) 0.2 220° 0.214. Tuscarora-Malpais 0.7

20.41.2

200° 0.41.1

15. Dry Hills 0.3m (recent)1.5 (penultimate)

0.20.9

220° 0.10.7

17. East Humboldt 2.3& 1.3 195° 1.3 E. 1915 Pleasant V. 2# (max 5.8) 1.2 200° 1.1

sum = 33.3 19.2 m 17.6sum (post 20 ka) = 21.5 12.4 m 11.3

The voyage to understanding… it’s a slow trip

~10 mm/yrOldow et al (2001)

~12 mm/yrSauber (1994)

11±1 mm/yrDixon et al. (2001)

6±2 mm/yrThatcher et al. (2001)

Individual Geodetic Arrays

Spanning the Walker Lane