Deformation during the 1975–1984 Krafla rifting crisis, NE Iceland, measured from historical optical imagery

Abstract

[1] We measure the displacement field resulting from the 1975-1984 Krafla rifting crisis, NE Iceland, using optical image correlation. Images are processed using the COSI-Corr software package. Surface extension is accommodated on normal faults and fissures which bound the rift zone, in response to dike injection at depth. Correlation of declassified KH-9 spy and SPOT5 satellite images reveals extension between 1977-2002 (2.5 m average opening over 80 km), while correlation of aerial photos between 1957-1990 provide measurements of the total extension (average 4.3 m opening over 80 km). Our results show $8 m of opening immediately north of Krafla caldera, decreasing to 3-4 m at the northern end of the rift. Correlation of aerial photos from 1957-1976 reveal a bi-modal pattern of opening along the rift during the early crisis, which may indicate either two different magma sources located at either end of the rift zone (a similar pattern of opening was observed in the 2005 Afar rift crisis in East Africa), or variations in rock strength along the rift. Our results provide new information on how past dike injection events accommodate long-term plate spreading, as well as providing more details on the Krafla rift crisis. This study also highlights the potential of optical image correlation using inexpensive declassified spy satellite and aerial photos to measure deformation of the Earth's surface going back many decades, thus providing a new tool for measuring Earth surface dynamics, e.g. glaciers, landsliding, coastal erosion, volcano monitoring and earthquake studies, when InSAR and GPS data are not available.

Origin of the compositional diversity in the basalt-to-dacite series erupted along the Heiðarsporður ridge, NE Iceland

“…We, nonetheless, concur that Fe-Ti rich basalts erupted along Heiðarsporður are similar to those found near the Krafla central volcano ( Fig. 3 and 4; Hollingsworth et al, 2012). Hence, we suggest that the Fe-Ti rich basalts in the Krafla volcanic system were also produced by differentiation and partial remobilization of cumulates following the production of large amounts of silicic magmas in the area in Refilled-Tapped-Fractionated (RTF) magma reservoirs in the upper Icelandic crust (e.g., Thorarinsson and Tegner, 2009).…”

“…They are very similar to the magmas sampled in the Krafla Central Volcano (see bulk rock geochemistry in supplementary materials), which have been erupted during the Krafla Fires between 1975 and 1984 (Hollingsworth et al, 2012). They have a vesicular, porphyritic texture and are more crystallized than olivine basalts.…”

Seismotectonics and rupture process of theMW 7.1 2011 Van reverse-faulting earthquake, eastern Turkey, and implications for hazard in regions of distributed shortening

“…We add further remote sensing observations and field evidence of the surface expression of this splay fault. In addition, we demonstrate the utility of two novel data sets in assessing and monitoring Quaternary and modern geomorphology within expanding cities-the exploitation of 1960s-1970s declassified US spy satellite imagery (Hollingsworth et al 2012); and the rapid, very low cost, photogrammetric mapping using Structure from Motion (SfM; James & Robson 2012;Johnson et al 2014).…”

The role of space-based observation in understanding and responding to active tectonics and earthquakes

“…4). This is achieved by using a method of sub-pixel correlation47, and these horizontal displacement fields can also be used to measure longer term tectonic motion48. Using a pair of 15 m panchromatic LANDSAT 8 images, the entire 220 km-long rupture in the M w 7.8 Baluchistan earthquake was captured in a single-image footprint49, with estimates of the far-field noise being ∼0.5 m.…”