MSGID: 1:317/3 6279eadc   
   PID: hpt/lnx 1.9.0-cur 2019-01-08   
   TID: hpt/lnx 1.9.0-cur 2019-01-08   
    Lake Erie quakes triggered by shifting water levels? Study finds no   
   smoking gun, urges further research    
      
     Date:   
         May 9, 2022   
     Source:   
         University of Michigan   
     Summary:   
         In June 2019, a magnitude 4.0 earthquake occurred beneath Lake   
         Erie just off the shoreline of Ohio, about 20 miles northeast   
         of Cleveland.   
      
      
      
   FULL STORY   
   ==========================================================================   
   In June 2019, a magnitude 4.0 earthquake occurred beneath Lake Erie just   
   off the shoreline of Ohio, about 20 miles northeast of Cleveland.   
      
      
   ==========================================================================   
   Though no damages were reported, the underwater quake was widely felt   
   up to 60 miles away -- throughout northeastern Ohio and in parts of   
   Pennsylvania, Ontario and southeastern Michigan.   
      
   The quake and numerous aftershocks occurred near the end of a period   
   of record- setting increases in Great Lakes water levels and coincided   
   with the highest water level ever recorded on Lake Erie. Could there be   
   a connection between Lake Erie seismicity and fluctuating water levels   
   in the lake?  To find out, University of Michigan researchers and their   
   colleagues compiled a new catalog of 437 relatively small Lake Erie-area   
   earthquakes that occurred between 2013 and 2020 -- the most complete such   
   catalog ever obtained. All of the quakes were smaller than the June 2019   
   event, and most were likely not noticed by residents of the region.   
      
   Then the researchers calculated the stresses that shifting Lake Erie   
   water levels would impart to faults in the rocks beneath the lake and   
   used various statistical methods to look for a correlation between   
   earthquake rates and water levels.   
      
   Their verdict?   
      
      
   ==========================================================================   
   "No conclusive correlation could be established between earthquake   
   rate and water level or water-level change rate," said U-M geophysicist   
   Yihe Huang, co- author of a study published online May 9 in the journal   
   Seismological Research Letters.   
      
   The lack of a smoking gun may be partly due to the limited number of   
   earthquakes in the new catalog, according to the researchers. Also,   
   Lake Erie- induced stress changes on nearby earthquake faults are likely   
   10s or 100s of times smaller than those seen in places -- such as the   
   reservoir behind India's massive Koyna Dam -- where earthquakes have   
   been blamed on changing water levels.   
      
   "We cannot fully rule out the impact of increasing water level on   
   reactivating the faults that hosted the 2019 Ohio earthquake sequence,"   
   said study lead author Dongdong Yao, a former U-M postdoctoral research   
   fellow who is now at China University of Geosciences.   
      
   "Our results highlight the necessity of denser and closer monitoring   
   of lake seismicity to further investigate the impact of changing water   
   loading on reactivating shallow faults in this region."  To follow up   
   on their findings, Huang and her colleagues will use novel techniques   
   to monitor Great Lakes regional seismology and will conduct physics-   
   based simulations. Specifically:   
       * Huang and U-M seismologist Zack Spica are planning a field   
       experiment   
         this summer to convert an existing fiber-optic cable in Lake Ontario   
         into sensors that can better monitor seismicity and other phenomena   
         such as seiches, bottom currents or water-level changes. Previous   
         studies in other parts of the country have demonstrated the   
         potential for using existing networks of fiber-optic cables --   
         the same optical fibers that deliver high-speed internet and HD   
         video to our homes -- to study earthquakes.   
      
       * Huang and colleagues will simulate the additional stresses on   
       Lake Erie-   
         area earthquake faults caused by high water levels, as well as   
         the degree to which lake water percolating into the bedrock may   
         help lubricate those faults. "These two effects may be competing   
         with each other in nature, and the physics-based simulations can   
         help us determine which effect is more important," she said.   
      
   In addition, Huang and her team are still analyzing data from a network   
   of eight seismometers, known as the LEEP project for Lake Erie Earthquake   
   exPeriment, that they operated in the western corner of Lake Erie from   
   October 2018 to July 2021.   
      
      
      
   ==========================================================================   
   The Great Lakes region is generally considered to be seismically inactive,   
   and earthquakes of magnitude 5 or greater are rare. However, earthquakes   
   with magnitudes greater than 2 occur two or three times a year in the   
   region, mainly around lakes Erie and Ontario. Earthquakes with magnitudes   
   of 2.5 to 3 are the smallest generally felt by people.   
      
   "We are not certain whether Lake Erie-area faults can produce destructive   
   or deadly earthquakes," said Huang, assistant professor in the U-M   
   Department of Earth and Environmental Sciences. "That's why seismologists   
   are interested in studying a magnitude 4-type earthquake sequence from   
   this region."  Since the early 2010s, eastern Ohio has seen a significant   
   increase in the frequency of relatively small earthquakes. The origins   
   of those earthquakes are poorly understood, but some previous studies   
   suggested they can be attributed to wastewater injection and hydraulic   
   fracturing activities.   
      
   Injection-induced seismicity has also been suggested as the trigger for   
   the region's last magnitude 5 earthquake, which occurred in January 1986   
   in northeastern Ohio, east of Cleveland in southern Lake County.   
      
   In the new study, which covers the period from 2013 to 2020, the U-M-led   
   team found a cluster of earthquakes in the vicinity of the 1986 temblor   
   and near wastewater disposal wells that were operating during the study   
   period. They concluded that this cluster of quakes "might be potentially   
   induced by wastewater disposal."  "More intriguingly, the 1986 earthquake   
   was also happening during another period of recorded high-water levels   
   across the Great Lakes," the authors wrote. "However, due to a large   
   distance relative to Lake Erie, it would be difficult to evaluate the   
   impact of lake-induced stress change on triggering the 1986 earthquake."   
   To create their new catalog of 437 Lake Erie-area quakes, the researchers   
   started with 27 previously reported earthquakes listed in the Advanced   
   National Seismic System Comprehensive Earthquake Catalog, which is known   
   as the ComCat catalog.   
      
   U.S. seismometer networks captured continuous recordings of ground motions   
   in the region during the study period. Using the waveforms produced by   
   the 27 known earthquakes as templates, the team scanned the continuous   
   recordings in search of previously undetected earthquakes with similar   
   waveforms. The process is called template matching.   
      
   Most of the earthquakes in the new catalog would not have been felt by   
   area residents and are only detectable by nearby seismometers sensitive   
   to tiny amounts of ground shaking.   
      
   The new catalog revealed 20 to 40 small earthquakes per year during the   
   study period, leading up to the June 2019 event. A high seismicity rate in   
   2019 was dominated by aftershocks following the magnitude 4.0 earthquake.   
      
   In addition to compiling the comprehensive new catalog, the team was   
   also first to map the fault that ruptured to produce the 2019 quake,   
   which occurred at a depth of roughly 2 kilometers (1.2 miles).   
      
   In addition to Yao and Huang, the authors of the Seismological Research   
   Letters paper are Liang Xue of Bowling Green State University and   
   Syracuse University, Yuning Fu of Bowling Green State University,   
   Andrew Gronewold of the University of Michigan Department of Earth and   
   Environmental Sciences and the School for Environment and Sustainability,   
   and Jeffrey Fox of the Ohio Department of Natural Resources. Funding to   
   Yao and Huang was provided by the University of Michigan.   
      
      
   ==========================================================================   
   Story Source: Materials provided by University_of_Michigan. Note:   
   Content may be edited for style and length.   
      
      
   ==========================================================================   
   Journal Reference:   
      1. Dongdong Yao, Yihe Huang, Liang Xue, Yuning Fu, Andrew Gronewold,   
      Jeffrey   
         L. Fox. Seismicity around Southern Lake Erie during 2013-2020   
         in Relation to Lake Water Level. Seismological Research Letters,   
         2022; DOI: 10.1785/ 0220210343   
   ==========================================================================   
      
   Link to news story:   
   https://www.sciencedaily.com/releases/2022/05/220509162412.htm   
      
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