Hi All. I have been looking at the Walker Lane/Eastern California Sheer Zone for a couple of years now and have found this stretch of faults to be fascinating at the very least. The term Walker Lane, Walker line, Walker belt, and Walker Lane belt are names applied to a generally north-northwest-trending linear zone of ranges lying between the Sierra Nevada on the west and northeast trending basin and ranges of the Basin and Range physiographic province on the east. Some descriptions of this belt note strike-slip faulting (mostly right-lateral) as a dynamic tectonic element. It is prominent part of the Eastern California Sheer Zone (ECSZ)

This broad zone is about 700 kilometers long with the southern most starting point near the Coso volcanic area (however I have a feeling that the recent Hector Mine quake may change this) and 80 to 240 kilometers wide. Stewart (1988) divided this belt into nine tectonic blocks, each with distinctive tectonic style. A somewhat more restrictive Walker Lane belt is that of Carr (1984), whose southwestern boundary is the northwest striking Death Valley-Furnace Creek-Fish Lake Valley fault zone, but his northeastern boundary is poorly defined as passing southeast across the Nevada Test Site with no physiographic or geologic definition.

Proponents: K.P. Furlong, T. Dixon, R. Bennett, , M. Miller

PROJECT SUMMARY

“The ECSZ serves as a major component of the Pacific ­ North America plate boundary,
accommodating 20-25% of the total plate rate. Over more than 500 km of plate boundary the displacement between the Pacific and North America plates is accommodated along two primary plate boundary shear zones ­ the San Andreas system and the ECSZ. On a transect perpendicular to Long Valley Caldera (LVC), the ECSZ is quite narrow but widens considerably to the south (and possibly north). We propose a continuous GPS transect utilizing ~ 20 CGPS instruments about 100 km south of LVC (slip primarily on two faults systems: Owens Valley and Death Valley-Furnace Creek). In combination with proposed arrays/transects in the LVC region, we can separate LVC from ECSZ tectonics. This transect crosses the middle of the rupture zone of the 1872 Owens Valley earthquake, allowing us to investigate the role of the earthquake cycle in surface strain pattern.

The present localization of strain and the deformational history of the ECSZ show patterns of strain partitioning within continental plate boundaries that can be exploited to place real constraints on the rheology of the plate boundary and the driving forces which lead to strain partitioning. Although the system is complex, the combination of detailed observations of present-day plate boundary deformation (including patterns of Quaternary faulting and regional geophysical data) with 3-D geodynamic modeling provides the means to discriminate among models of plate boundary deformation. We propose new GPS observations and geodynamical modeling to test the following hypotheses:

Hypothesis 1: The ECSZ represents a throughgoing plate bounding shear zone, fully
analogous to a plate boundary, and may soon (next few million years) develop into the main plate boundary as the plate boundary continues to migrate inland and the San Andreas is abandoned.

Hypothesis 2: The localization of strain producing the ECSZ is controlled by a relatively
abrupt change in viscosity from higher values beneath the Sierra Nevada block to lower
values within the western Basin and Range, reflected in surface heat flow.

Hypothesis 3: The motion of the Sierra Nevada ­ Great Valley tectonic block (~ 12-14 mm/yr relative to stable North America) is driven by the combination of shear coupling along the San Andreas plate boundary shear zone and forces produced through convergence in the Transverse Ranges.

Hypothesis 4: Initiation of the ECSZ was primarily driven by the opening of the Gulf of
California (~ 4-8 Ma). The development of the Transverse Ranges may reflect either a cause or an effect of the formation of the ECSZ.”

The ECSZ continues north in the region between the Sierra Nevada and the California-Nevada border into eastern Oregon, possibly connecting with the Cascade Range (Pezzopane and Weldon, 1993; Miller et al, 1998). It is thought that one day it may even end up in British Colombia.

There have been a couple of earthquake swarms in Eastern Oregon that may have been caused by the ECSZ. Most particularly those that were located near Newberry volcano Oregon.

This of course brings the Three Sisters Volcaonos to mind. To date I have been unable to locate any earthquakes, or earthquake swarms in the area of the bulge west of South Sister.

However I did find some evidence that large earthquakes elsewhere can an do have an affect on areas of volcanic activity and has been reported by David Hill of USGS.

“Film was also scanned for the 24 hours following the M 7.0 earthquake at 40.37°N, 124.32°W (near Cape Mendocino) on 25 April. Although smaller than the 28 June earthquake, its epicenter was only 20-25% as far from the volcanoes. Furthermore, both the 25 April main shock and a M 6.5 aftershock were felt at the volcanic centers, but no felt reports were received from these areas after the 28 June earthquake. Only the Geysers showed any possible triggered events after the 25 April shock. However, background seismicity at the Geysers is higher than at the other centers, and is influenced by fluid injection and withdrawal associated with intensive geothermal development.

Medicine Lake Report. Twelve events were detected in the Medicine Lake area (~900 km NNW of the epicenter) in the 30 minutes after the M 7.5 earthquake. All had coda durations less than or equal to 10 seconds. The lack of any S-P separation indicated that they were centered very close to the single seismic station, near the center of the caldera.”
There is a connection to all things and all things have a connection to one another. We may not see it, but that doesn’t mean that there is no connection. Take Care…Don in creepy town.