Rit (Vísindafélag Íslendinga) - 01.06.1971, Side 58

58
GUÐMUNDUR PÁLMASON
the southern profile. A correlation hetween the gravity data and the
seismically determined structure is also evident here. The depth
change to layer 3 on Skógaströnd is reflected in the gravity data by
a change in gravity of about 5 milligals. Farther to the west the
gravity values also show some correlation with the seismic structure.
Gravity highs correspond to shallow depth to layer 3. Because of the
complexity of the structure in this area it is not possible from the
limited amount of data availahle to make calculations of the density
difference causing these gravity anomalies.
For a brief discussion on amplitude relationships of refracted
waves on the Stykkishólmur—Ólafsvík profile, see section 7.
6.6. NW-Peninsula.
Only three profiles are available on the NW-peninsula. Two of
them, Patreksfjördur (62) and Amarfjördur (63) are on the westem-
most part of the peninsula and are unreversed. One reversed profile,
Kaldalón—fsafjördur (64a and 64b), is located in the central part of
the peninsula.
Profiles 62 and 63 show a fairly regular stmcture indicating the
existence of both layers 1 and 2. Layer 1 has a somewhat higher than
normal apparent velocity on profile 62, ahout 4.7 km/sec, possibly
caused by a thin low-velocity surface layer near the shot point. The
total delay times for the P3-wave are shown in Fig. 19. In Amar-
fjördur the delay time is increasing from NW to SE, while in Pat-
reksf jördur the profile is too short to give more than an indication of
the dip of the 2-3 interface. Depth estimates to layer 3 give in Amar-
fjördur 3.7 km near the northwest end of the profile increasing to 4.5
km near the southeast end. In Patreksfjördur a depth of about 4.8 km
is indicated.
The profiles 64a and 64b show a somewhat different stracture.
Layer 2 is at or very close to the surface with apparent velocities of
4.95 and 5.0 km/sec. A positive travel time anomaly is found on hoth
profile directions just north of Nauteyri. The anomaly extends over
several km, but its maximum is near the farm Hafnardalur. It is
probahly caused by a local occurrence of a lower-velocity surface
layer, perhaps layer 1. Layer 2 is underlain by material with an ap-
parent velocity of about 5.5 km/sec on hoth profile directions. The
profiles, which are about 32 km, are not sufficiently long to record
waves with a higher velocity. The existence of a layer with a P-wave