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Apr 06, 2023 143 likes •341 views

The submarine landscape of the Mediterranean Israeli continental slope Oded Katz 1 , Einav Reuven 1,2 , Einat Aharonov 2 1. Geological Survey of Israel 2. The Hebrew University of Jerusalem, Israel This work: -3 LS Water Step We study the

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The submarine landscape of the Mediterranean Israeli continental slope

Oded Katz1, Einav Reuven1,2, Einat Aharonov2

1. Geological Survey of Israel
2. The Hebrew University of Jerusalem, Israel

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This work: We study the bathymetry and near surface geology off the coast of Israel. This is now feasible due to a recently released bathymetry grid:

National bathymetric grid – IOLR,

GSI (Sade et al., 2006, 2008);

Resolution: 15 m grid till water

depth of 700 and 50 m grid till water depth of 1750 m.

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Water depth (m) Haifa Hadera Tel Aviv Ashdod Ashqelon Natanya 40 km LS Step

Motivation:

1. Connecting surface geomorphic

features to past and present geological processes;

2. Hazard evaluation (landslides,

active faulting).

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Studied area: Israeli continental slope, water depth range 100 – >1000 m. Objectives of the work:

1. Mapping landslides and related

surface features (steps trenches);

2. Analyzing landslide mechanics,

slope stability and triggering conditions;

3. Hazard mapping (seismic and

infrastructure related: gas lines and facilities).

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Water depth (m) Haifa Hadera Tel Aviv Ashdod Ashqelon Natanya 40 km LS Step

Previous works: Almagor and Garfunkel, 1979; Almagor, 1983; Garfunkel and Almagor, 1985; Gradmann et al., 2005; Mart and Ryan, 2007; and more.

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Funding:

Steering Committee for Earthquake Preparedness, Israel (2011-

12) - to GSI;

Ministry of Science and Technology (2012-2014):
1. Katz, O. (GSI), Aharonov, E. (HU), Klar, A. (Technion);
2. Makovsky, Y. (UH), Tibor, G. (IOLR), Kamishny, A. (BGU).

ןוינכטה

לארשיל יגולונכט ןוכמ

הטיסרבינואה תירבעה םילשוריב

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A A’

x10 vertical exaggeration No vertical exaggeration

Continental slope off the Israeli coast

Haifa TA Ashdod

A A’

Slope = 4° Water depth (m)

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Canyon Land Open Slope with landslides

Continental slope offshore Israel;

Haifa Tel Aviv Ashdod Hadera

(Why are there two provinces of different behavior?)

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Palmahim disturbance Dor disturbance

Large geomorphic features

(e.g. Almagor & Garfunkel, 1979)

Haifa Tel Aviv Ashdod Hadera

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15 km 10 km

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Geological structure (Almagor and Garfunkel, 1979)

1. Pliocene-Quaternary silt and clay 2. Messinian evaporites

1 2

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Gradmann et al., 2005

Salt tectonic offshore Israel

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Similarity of landslides geometry: t/l ~ 0.1 e.g. Klar, Aharonov, Katz, 2011

t l

Thus: Palmahim disturbance: l ~ 10 km → t ~ 1 km Shallow landslides: l ~ 1 km → t ~ 0.1 km

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Mapping targets (south of Haifa): 1. Landslides (scars and deposits); 2. Step like lineaments (growth faults); 3. Trenches

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Haifa Hadera Natanya Tel Aviv Ashdod Ashqelon

>15.0° 10.0° 7.5° 12.5° 2.5° 5.0° 0.0°

Slope angle

34.0° E 32.0° N 35.0° E 33.0° N

Landslide Step/channel

50 km 25

Slope Map with mapped landslides

In this talk:

Map of submarine landscape

in the area south of Haifa.

This talk

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Simple landslide

500 1000 1500 Distance (m) Water depth (m)

1:2 vertical exaggeration

A A’ Slope = 15°

1 km

Step Toe Scar Step Scar Step Scar Toe Step Scar

~50 m

A A’ Map view Perspective view N S W E

Simple (and apparently younger) landslide

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500 1000 1500 2000 Distance (m) Water depth (m)

Scar Step 2 km Scar Scar Step Complex landslide

1:2 vertical exaggeration A A’ Slope = 25° A’ A N S N S

Complex (and apparently older) landslide

Map view Perspective view

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Landslide Step/channel Haifa Hadera Tel Aviv Ashdod Ashqelon Natanya 40 km 5 km

Map view E W Perspective view S N

Large landslide

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Landslide Step/channel Haifa Hadera Tel Aviv Ashdod Ashqelon Natanya 40 km

Steps (growth faults)

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Step Step Step Step Step

~60 m ~85 m

2 km

Map view

Perspective view

E W S N

Steps (growth faults) A A’

Base Pliocene

Base Messinian

Line 2057-IS

A A’

Fault interpretation: Ecolog

W E

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Trench

~40 m

Perspective view E W

4 km

Map view E W

Channel

Landslide Step/channel Haifa Hadera Tel Aviv Ashdod Ashqelon Natanya 40 km

Base Pliocene

Base Messinian

Line 2057-IS

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Summary

Slides become smaller northwards, and are

characteristic of the southern province.

Landslides, both young and old, either

emerge from the over-steepened steps (growth faults), or are displaced by them, and hence submarine landslides and steps are apparently contemporaneous. These slides are smaller and different than the two main disturbances, Palmahim and Dor.

Salt dynamics at depth is a main drive for at

least some of the shallow landslides.

The above preliminary results testify to the

complicated and highly dynamic nature of the studied continental slope, yet to be

revealed. Future finding are relevant to the

energy industry and infrastructure as well as to general seismic hazard analysis and regulations.

Landslide Step/channel Haifa Hadera Tel Aviv Ashdod Ashqelon Natanya 40 km

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