Classifying marine faults for hazard assessment offshore Israel: a new approach based on fault size and vertical displacement
<p>For many countries, the methodology for offshore geohazard mitigation lags far behind the well-established onshore methodology. Particularly complicated is the assessment of fault hazard in the marine environment. The determination of whether a fault is active or not requires ultra-high-res...
| Main Authors: | , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2023-01-01
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| Series: | Natural Hazards and Earth System Sciences |
| Online Access: | https://nhess.copernicus.org/articles/23/139/2023/nhess-23-139-2023.pdf |
| Summary: | <p>For many countries, the methodology for offshore geohazard mitigation lags far behind the well-established onshore methodology. Particularly
complicated is the assessment of fault hazard in the marine environment. The determination of whether a fault is active or not requires
ultra-high-resolution seismic surveys and multiple coring and, unfortunately, frequently ends with uncertain results. Moreover, if a pipeline must
cross a fault, it is not enough to determine whether the fault is active; slip rates are needed for resistant planning.</p>
<p>Here we suggest a new approach for fault hazard assessment for the master planning of infrastructure. We provide planners a way to choose a route
that will cross the least hazardous faults; these faults will then be investigated in site-specific surveys for slip rates that will allow seismic
design. Instead of following the onshore practice that is hard to implement in the marine environment, we suggest taking advantage of the marine
environment where seismic data are commonly better in quantity and quality. Based on existing industrial 3D seismic surveys, we measure for each
fault in the study area the amount of its recent (in our specific case, 350 <span class="inline-formula">ka</span>) vertical displacement and the size of its plane. According
to these two independently measured quantities, we classify the faults into three hazard levels. This allows planners to choose infrastructure
routes that cross the least hazardous faults at an early stage of planning and direct them to sites that need further investigation.</p>
<p>Our case study is the Israeli continental slope, where numerous salt-related, thin-skinned, normal faults dissect the seabed, forming tens of meters
high scarps. A particular hazardous zone is the upper slope south of the Dor disturbance, where a series of big listric faults rupture the seabed in
an area where the sedimentation rate is 4 times faster than the vertical displacement rate. We suggest that this indicates exceptionally fast
creep, seismic rupture, or rapid tremor and slip episodes.</p> |
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| ISSN: | 1561-8633 1684-9981 |