Geodetic GPS measurements in south Iceland: Strain accumulation and partitioning in a propagating ridge system

Abstract

[1] GPS observations in south Iceland between 1994 and 2003 are compared with twodimensional elastic half-space and viscoelastic coupling models for two parallel rift zones, representing the Western and Eastern volcanic zones (WVZ, EVZ). GPS data from the Hreppar block, between the WVZ and EVZ, fit a rigid block model within uncertainties. Spreading rates across the WVZ increase from 2.6 ± 0.9 mm/yr in the northeast to 7.0 ± 0.4 mm/yr in the southwest. Conversely, spreading rates in the EVZ decrease from 19.0 ± 2.0 mm/yr in the northeast to 11.0 ± 0.8 mm/yr in the southwest, the direction of ridge propagation. Summed extension rates across the two rift zones are approximately constant and equal to the total plate rate, $18-20 mm/yr, consistent with a simple propagating ridge model whereby the WVZ is deactivating in the direction of EVZ propagation. The coupling model confirms results from the simple elastic half-space model, including relatively shallow locking depths (<5 km) beneath the rift zones, and allows for an estimate of mean viscosity ($10 19

Brittle tectonics of the Thingvellir and Hengill volcanic systems, Southwest Iceland: field studies and numerical modeling

“…Current geodetic measurements indicate that the total opening rate of the WVZ varies from 3-8 mm/year, being greatest in the southwest and decreasing northeast along the zone [14,16,21]. Since the total spreading rate in South Iceland is 18.5 mm/year, it implies that only 16-43 % of the spreading rate is due to opening of the WVZ.…”

“…The proximal location of the Icelandic hot spot and a west-northwest motion of the MOR relative to the hot spot since 20 Ma, promoted the development of overlapping spreading centres through repeated ridge jumps and ridge propagation [14]. Furthermore, it generated two transform zones: Tjörnes Fracture Zone in north and South Iceland Seismic Zone (SISZ) in south Iceland [15].…”

The development of extension and magmatism in the Red Sea rift of Afar

“…In Afar for example, we currently lack detailed geodetic constraints across the present day plate boundary zone, such geodesy campaigns are routine in Iceland, for example (e.g., Arnadottir et al, 2009;LaFemina et al, 2005). Also of fundamental importance to understanding rates of decompression melting and margin subsidence are improved constraints on the variation of lithospheric thickness over time during the rifting to spreading process (e.g., Huismans and Beaumont, 2011).…”

The propagation of seafloor spreading in the southwestern subbasin, South China Sea

“…On the basis of publications over recent years, propagating rifting and spreading also occur at modern slow-spreading mid-ocean ridges and back-arc spreading centers (e.g. the Mid-Atlantic Ridge (MAR) [9], but there is no evidence for propagating spreading at ultra-slow spreading mid-ocean ridges (e.g. the Southwest Indian Ridge (SWIR)).…”

“…The Southeast Indian Ridge propagates from WNW to ESE, but there is a big difference in propagation rate (7-49 mm/a). In the Atlantic Ocean, only the regions north of Iceland (34°-46°S; 75°-98°W) and south of 30°S show southwestward propagation, but each part has its own propagation direction and rate [5,9].…”