Sand Blows SB1 and SB2 in Trench T3
Kanari et al. (2020) report that Trench T3,
excavated across the active
Avrona Fault in the
Elat Sabkha, contains two large
sand blows (SB1 and SB2) west of the mapped
fault rupture. These features represent
liquefaction
rather than direct
surface faulting.
Kanari et al. (2020) describe SB1 as a large
mound (up to ~5 m in diameter and ~1 m high) of
unstratified sand that has torn through overlying
silt, clay, and clayey silt layers, incorporating
them as
rip-up clasts
and redepositing them outward from the center of
the feature. The sand body is capped by Layer L3.
Sand blow SB2 has a similar
morphology,
with a mound of unstratified sand flanked by
fine-grained sediments sloping away from
vent.
In both cases,
feeder dikes were not identified,
leading
Kanari et al. (2020) to interpret these as
shallow-sourced liquefaction features rather than
deep injection structures.
Kanari et al. (2020) constrain the age of these
features using
radiocarbon dating
of material beneath and within the sand blows but not above.
Modeling of these data yields a probability range
for liquefaction between
1287 and 1635 CE. Two of the four radiocarbon samples were rejected—
one (ET3 135), which was interpreted as an
outlier, and another (ET3 134), which
yielded an apparently reasonable
2σ calibrated age range of 1256–1385 CE but
was excluded because it did not conform to the
model. By estimating a
sediment accumulation rate and
the depth to the capping horizon, they infer
that burial of the feature began prior to
~1550 CE, thereby further constraining the event to
approximately 1287–1550 CE.
Kanari et al. (2020:12–14) interpret SB1 and
SB2 as earthquake-induced
paleoliquefaction
that may be contemporaneous with the second
faulting event (E2) identified in Trench T3. They
suggest that these data are most consistent with
correlation to the
1458 CE earthquake, noting that "these data
tend to support an interpretation of 1458 CE, but
are inconclusive." Alternatively, the features
could relate to the
1588 CE earthquake, or another event within
the same time window. Thus, SB1 and SB2 record
strong seismic shaking in the Elat Sabkha after
1287 CE and likely before ~1550 CE, probably
associated with the same earthquake that produced
Event E2, but without sufficient resolution to
distinguish definitively between candidate
historical earthquakes.
