Velocities derived from data spanning August 1, 2000 to December 31, 2001

To exclude the effects of the Hekla 2000 eruption and coseismic displacements at HLID due to the June 2000 SISZ earthquake sequence a third set of velocities is calculated (Table 8, Figures 26 and 27) using data only after August 1, 2000, until December 31, 2001. It is not necessary to correct for any offsets, except for an offset due to a instrumental change at HOFN in September 2001 (Table 2). The results are expected to be the same as in Tables 6 and 7 for stations that were installed after August 1, 2000 (AKUR, KIDJ, RHOF and SKRO).

The velocities obtained in this section can be interpreted as interseismic velocities at the stations. Most stations are moving at velocities similar to the NUVEL-1A plate motion model, except for the stations SOHO and HVOL near Mýrdalsjökull and in the Hengill area (Figure 27). The velocities are similar to the ones obtained in the previous section (Table 7), except for SOHO, HVOL and HLID.

The stations HLID, HVER, OLKE and KIDJ are within the plate boundary deformation zone moving at intermediate velocities. Station VOGS is moving at almost the NUVEL-1A rate, HLID is on the Eurasian side of the plate boundary, and HVER is on the North-American side of the plate boundary. OLKE is moving at nearly the NUVEL-1A rate for the North-American plate. There are only 15 km between HLID and HVER and the present location of the plate boundary is confined between the stations.

KIDJ is moving almost due north. KIDJ is within the SISZ, approximately 5 km west of the Hestfjall fault which ruptured on June 21, 2000 (Figure 27). Thus postseismic movements at the right lateral Hestfjall fault might be affecting the movement of KIDJ.

 

Table 8: Calculated velocities of the stations in east, north and up, relative to REYK, using data from August 1, 2000, as of December 31, 2001. See Table 6 for explanation of the columns.

		Velocities [mm/yr]			Uncertainties [mm/yr]			WSTD [mm]			Chi squared
Station	N	Ve	Vn	Vu	dVe	dVn	dVu	e	n	u	$\chi^{2}_{\nu e}$	$\chi ^{2}_{\nu n}$	$\chi^{2}_{\nu u}$
AKUR	102	-5.5	4.9	3.0	2.5	3.1	12.8	1.3	1.7	7.0	1.7	1.2	1.8
HLID	252	13.3	-2.6	5.7	0.4	0.5	1.8	1.1	1.3	4.9	1.4	0.8	0.9
HOFN	447	20.2	-6.5	7.1	0.5	0.4	1.5	2.2	1.8	6.4	2.6	1.7	1.5
HVER	487	6.4	-0.7	0.8	0.3	0.3	1.1	1.3	1.4	5.0	2.2	1.0	0.9
HVOL	453	19.6	-7.7	6.0	0.3	0.4	1.4	1.4	1.8	6.3	2.0	1.6	1.3
KIDJ	330	10.2	2.5	5.4	0.4	0.5	2.0	1.0	1.1	4.8	1.3	0.7	0.9
OLKE	464	3.7	-1.3	5.5	0.3	0.4	1.1	1.4	1.7	4.6	2.5	1.7	0.9
RHOF	128	18.0	0.1	-6.2	2.5	2.8	10.5	1.6	1.8	7.1	1.8	1.1	1.6
SKRO	416	2.7	1.1	16.1	0.5	0.5	2.4	1.8	1.6	8.4	3.1	1.4	2.7
SOHO	469	18.3	-11.2	6.0	0.4	0.5	1.5	1.6	2.0	6.2	2.7	1.9	1.3
THEY	462	21.0	-4.3	2.3	0.3	0.4	1.5	1.4	1.8	6.3	2.2	1.6	1.5
VMEY	493	20.0	-6.1	3.9	0.3	0.3	1.2	1.3	1.3	5.1	1.8	0.9	0.9
VOGS	487	16.9	-3.1	5.5	0.3	0.3	1.0	1.1	1.3	4.6	1.6	0.8	0.8

 

  

Figure 26: Velocities for the permanent GPS stations, as in Table 8, assuming REYK is moving at velocity 9.6 mm/yr west and 2.1 mm/yr north (black arrows) compared to the NUVEL-1A plate motion model velocities (orange arrows). The velocities are based on data spanning the period August 2000 to January 2002. Confidence limits are at the 2$\sigma$ level.

  

Figure 27: As in Figure 26 for the Hengill area. Red line shows the location of the fault that ruptured in the June 21, 2000, earthquake according to [Árnadóttir et al. (2001)].