Seismicity. Induced seismicity of high intensity was unknown in the Húsmúli area. However, already during drilling of xxxxx in the Húsmúli formation, seismicity occurred when intersecting permeable formations or the bottom of the feed zones with maximum magnitudes of ML 2.5 [16]. Production tests have furthermore caused seismic events as well as swarms of earthquakes that were registered after commission of the field in September 2011 with two magnitude 4 earthquakes. The seismicity during operation is thought to be caused by the injections lowering the effective pressure and thus friction on faults and by mass extraction causing subsidence [17]. It is furthermore related to the temperature of the injected water, as seismicity is higher with cold water. Furthermore there is a temporal trend, as seismicity ceased with time, indicating a release of stress. Finally, with increasing injection rate (l/s) the seismicity is increasing [17]. The orientation of the registered seismic events is contradicting the orientation of the NE-SW trending swarm of fissures in the Húsmúli area and is probably related to the orientation of the South Iceland Seismic Zone, where most of the strike-slip faults are N-E oriented.
Seismicity. Over the past 500 years, the region around St. Gallen experienced seismicity, however not particularly along the fault in the target region. The closest seismic event was an earthquake in 1987 with a magnitude of ML 3.2 located near the town of Abtwil, WNW of St. Gallen [23]. The distance between the epicenter of the 1987 earthquake and the 2013 St. Gallen earthquake is about 2 km. A normal faulting regime was observed at the 1987 earthquake [20]. Due to the lack of recent seismic activity the public utility company of St.Gallen, project operator St. Galler Stadtwerke, concluded that the fault zone is hardly seismically active [24]. However, during the step-rate injection test 12 micro-earthquakes were detected with magnitudes ML <= 0.9, followed by seismic events in vicinity of the injection with magnitudes ML <= 1.2 during the acidization, and further increasing seismicity with the ML 3.5 event during the well control operation after the gas kick. The focal mechanism of event indicates a strike-slip faulting regime with the maximum principal stress in NNW-SSE. [25] relocated the seismicity around the St. Gallen site and concluded that the majority of earthquakes (more than 800 events in 2013) is „[...] located in the pre-Mesozoic basement, likely within a Permo- Carboniferous trough below the targeted hydrothermal aquifer.“ This supports the possibility that the gas migrated upward from the Permo-Carboniferous trough [26].
Seismicity. According to revised IS-1843/2002, the gravity canal falls within the zone-2 of the Seismic Zone Map of India (Plate-5) which means that the area has very low damage risk. Although the proposed area falls under low damage risk one without potential threat to the structures, precautions have been taken for earth quake resistant design of major structures like aqueducts, Super passages, bridges etc. Considering an important factor of 3, the horizontal seismic coefficient is taken as 0.05g and vertical seismic coefficients as 0.10g
Seismicity. The regional seismic activity of the area could be considered as moderate with magnitude less than 5.0 (Mezcua et al., 1992), and mainly concentrated between the two major islands (Tenerife and Gran Canaria). During 2004 the island of Tenerife experienced a seismic crisis with more than 2000 recorded events (more than 350 located and 5 felt by the population) (xxx.xxx.xx) which were considered evidence of a volcanic reactivation after almost 100 years of calm (Xxxxx et al., 2009 and references therein). This crisis produced a significant social impact due to the high population of the island and the previous long repose periods in volcanic activity on Tenerife. Figure 20 shows the seismicity from 2004 to 2016 located by the IGN (xxx.xxx.xx).
Seismicity. Regional Local earthquake effects Ground rupture potential Liquefaction potential Lateral spreading potential Potential for ground lurching Potential for Tsunami Potential for seiche Seismically included land sliding or rockfall RECOMMENDATIONS
1. Methods of excavation by equipment and/or blasting
2. Slope ration (H:V) and maximum height of temporary cut slopes during construction
3. Stabilization of interim cut slopes (if necessary)
4. Slope ratio (H:V) and maximum height of temporary cut slopes during construction
5. Shoring load, slope gradients, and stabilization of temporary cut slopes
6. Slope ratio (H:V) and maximum height of fill slopes
7. Key and bench recommendations for constructing fill slopes 8. Terrace drains and down drains 9. Removal of unsuitable material 10. Disposal of oversized material 11. Preparation of natural ground to receive fill 12. Suitability of native soils for use as backfill
Seismicity. In identifying and evaluating all potential threats to each pipe- line segment pursuant to parts 192 and 195 of title 49, Code of Federal Regulations, an operator of a pipeline facility shall con- sider the seismicity of the area.
