Jökull - 01.12.1989, Page 40

10542.62- 7724.74 - 6969.94 -
10542.60 ■ 7724.72 - i 6969.92 -
10542.58 ■ 7724.70 - 6969.90 -
10542.56 - 7724.68 - I 6969.88 -
1976' ‘ 78 ' ' 80 ' ' 82 ' FLÓI 1 - 2 ' 84 A.D. 1976' ' 78 ' 80 82 FLÓI 1 - 3 84 .D.
1976 78
Fig. 6. Measured line lengths in the Flói network as a function of time. Numbers refer to Fig. 2. Vertical
bars show the standard deviations of the observations.
Mynd 6. Mœlingar í Flóa. Mœldar lengdir sýndar semfall af tíma. Lóðrétt strik sýna staðalfrávik mœling-
anna.
S 8121.26 ■ ° 8121.24- 8121.22 ■ 8121.20 - 5 12012.98- i 12012.96 - 12012.94 - 12012.92 - □
1979 80 ' 81 82 ' 83 HOLT 1-2 ^ □ 84 ' A.D. M 9793.86 9793.84 I 9793.82 9793.80 1979 80 ' 81 82 ' 83 HOLT 1-3 i 84 A.D. M 4874.64 4874.62 ^ 4874.60 - 4874.58 1979 80 ' 81 82 ' 83 ' 84 HOLT 1-4 í □ □
1979 80 81 82 83 84 A.D. 1979 80 81 82 83 84 A.D. HOLT 2-3 HOLT 2-4 1979 80 ' 81 82 ' 83 ' 84 HOLT 3-4
Fig. 7. Measured line lengths in the Holt network as a function of time. Numbers refer to Fig. 2. Vertical
bars show the standard deviations of the observations.
Mynd 7. Mœlingar í Holtum. Mældar lengdir sýndar semfall aftíma. Lóðrétt strik sýna staðalfrávik mœling-
anna.
time, of the order of decades, may be needed to
establish the average, long-term strain rate across
the boundary.
The strain loading may even be partly discontinu-
ous and dependent on processes extemal to the zone
itself. At least two of the historical earthquake
sequences, those of 1732-34 and 1784, occurred
immediately after major rifting episodes in the rift
zones. The 1732-34 earthquakes followed the Mý-
vatn Fires in North Iceland, that began in 1724 with
a large rifting event and culminated in 1728-29
with a considerable lava extrusion. The 1784 earth-
quake followed the gigantic 1783 lava eruption at
Laki in SE-Iceland. These rifting episodes involved
at least 30 km long, and possibly as much as 70 km
long sections of the rift zones. Rifting on that scale
38 JÖKULL, No. 39, 1989