Update on the seismogenic potential of the Upper Rhine Graben southern region
<p>The Upper Rhine Graben (URG), located in France and Germany, is bordered by north–south-trending faults, some of which are considered active, posing a potential threat to the dense population and infrastructures on the Alsace plain. The largest historical earthquake in the region was the &l...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2024-01-01
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| Series: | Natural Hazards and Earth System Sciences |
| Online Access: | https://nhess.copernicus.org/articles/24/163/2024/nhess-24-163-2024.pdf |
| Summary: | <p>The Upper Rhine Graben (URG), located in France and Germany, is bordered by north–south-trending faults, some of which are considered active, posing a potential threat to the dense population and infrastructures on the Alsace plain. The largest historical earthquake in the region was the <span class="inline-formula"><i>M</i>6.5±0.5</span> Basel earthquake in 1356. Current seismicity (<span class="inline-formula"><i>M</i>>2.5</span> since 1960) is mostly diffuse and located within the graben. We build upon previous seismic hazard studies of the URG by exploring uncertainties in greater detail and revisiting a number of assumptions. We first take into account the limited evidence of neotectonic activity and then explore tectonic scenarios that have not been taken into account previously, exploring uncertainties for <span class="inline-formula"><i>M</i><sub>max</sub></span>, its recurrence time, the <span class="inline-formula"><i>b</i></span> value, and the moment released aseismically or through aftershocks. Uncertainties in faults' moment deficit rates, on the observed seismic events' magnitude–frequency distribution and on the moment–area scaling law of earthquakes, are also explored. Assuming a purely dip-slip normal faulting mechanism associated with a simplified model with three main faults, <span class="inline-formula"><i>M</i><sub>max</sub></span> maximum probability is estimated at <span class="inline-formula"><i>M</i><sub>w</sub></span> 6.1. Considering this scenario, there would be a 99 % probability that <span class="inline-formula"><i>M</i><sub>max</sub></span> is less than 7.3. In contrast, with a strike-slip assumption associated with a four-main-fault model, consistent with recent paleoseismological studies and the present-day stress field, <span class="inline-formula"><i>M</i><sub>max</sub></span> is estimated at <span class="inline-formula"><i>M</i><sub>w</sub></span> 6.8. Based on this scenario, there would be a 99 % probability that <span class="inline-formula"><i>M</i><sub>max</sub></span> is less than 7.6.</p> |
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| ISSN: | 1561-8633 1684-9981 |