Item talk:Q266591

{

 "USGS Publications Warehouse": {
   "@context": "https://schema.org",
   "@type": "Article",
   "additionalType": "Journal Article",
   "name": "Geologic evidence of earthquakes at the Snohomish Delta, Washington, in the past 1200 yr",
   "identifier": [
     {
       "@type": "PropertyValue",
       "propertyID": "USGS Publications Warehouse IndexID",
       "value": "70185086",
       "url": "https://pubs.usgs.gov/publication/70185086"
     },
     {
       "@type": "PropertyValue",
       "propertyID": "USGS Publications Warehouse Internal ID",
       "value": 70185086
     },
     {
       "@type": "PropertyValue",
       "propertyID": "DOI",
       "value": "10.1130/0016-7606(2001)113<0482:GEOEAT>2.0.CO;2",
       "url": "https://doi.org/10.1130/0016-7606(2001)113<0482:GEOEAT>2.0.CO;2"
     }
   ],
   "journal": {
     "@type": "Periodical",
     "name": "Geological Society of America Bulletin",
     "volumeNumber": "113",
     "issueNumber": "4"
   },
   "inLanguage": "en",
   "isPartOf": [
     {
       "@type": "CreativeWorkSeries",
       "name": "Geological Society of America Bulletin"
     }
   ],
   "datePublished": "2001",
   "dateModified": "2022-10-13",
   "abstract": "Exposed channel banks along distributaries of the lower Snohomish delta in the Puget Lowland of Washington reveal evidence of at least three episodes of liquefaction, at least one event of abrupt subsidence, and at least one tsunami since ca. A.D. 800. The 45 measured stratigraphic sections consist mostly of 2\u20134 m of olive- gray, intertidal mud containing abundant marsh plant rhizomes. The most distinctive stratigraphic unit is a couplet comprising a 0.5\u22123-cm-thick, laminated, fining-upward, tsunami-laid sand bed overlain by 2\u221210 cm of gray clay. We correlated the couplet, which is generally \u223c2 m below the modern marsh surface, across an \u223c20 km2\u00a0area. Sand dikes and sand-filled cracks to 1 m wide, which terminate upward at the couplet, and sand volcanoes preserved at the level of the sand bed record liquefaction at the same time as couplet deposition. Differences in the type and abundance of marsh plant rhizomes across the couplet horizon, as well as the gray clay layer, suggest that compaction during this liquefaction led to abrupt, local lowering of the marsh surface by as much as 50\u201375 cm. Radiocarbon ages show that the tsunami and liquefaction date from ca. A.D. 800 to 980, similar to the age of a large earthquake on the Seattle fault, 50 km to the south.We have found evidence for at least two, and possibly as many as five, other earthquakes in the measured sections. At two or more stratigraphic levels above the couplet, sand dikes locally feed sand volcanoes. Radiocarbon ages and stratigraphic position suggest that one set of these dikes formed ca. A.D. 910\u2013990; radiocarbon ages on a younger set indicate a limiting maximum age of A.D. 1400\u20131640. We also interpret a sharp lithologic change, from olive-gray, rhizome-rich mud to grayer, rhizome-poor mud, \u223c1 m above the couplet, to indicate a second abrupt lowering of the marsh surface during an earthquake ca. A.D. 1040\u2013 1400, but no conclusive liquefaction structures have been identified at this horizon. Two distinctive coarse-sand laminae, 30\u201380 cm below the couplet, may record tsunamis older than A.D. 800.Thus, study shows that in the past \u223c1200 yr, this part of Washington's Puget Lowland has been subjected to stronger ground shaking than in historic times, since ca. 1870.",
   "description": "7 p.",
   "publisher": {
     "@type": "Organization",
     "name": "Geological Society of America"
   },
   "author": [
     {
       "@type": "Person",
       "name": "Johnson, Samuel Y. sjohnson@usgs.gov",
       "givenName": "Samuel Y.",
       "familyName": "Johnson",
       "email": "sjohnson@usgs.gov",
       "identifier": {
         "@type": "PropertyValue",
         "propertyID": "ORCID",
         "value": "0000-0001-7972-9977",
         "url": "https://orcid.org/0000-0001-7972-9977"
       },
       "affiliation": [
         {
           "@type": "Organization",
           "name": "Pacific Coastal and Marine Science Center",
           "url": "https://www.usgs.gov/centers/pacific-coastal-and-marine-science-center"
         }
       ]
     },
     {
       "@type": "Person",
       "name": "Bourgeois, Joanne",
       "givenName": "Joanne",
       "familyName": "Bourgeois"
     }
   ],
   "spatialCoverage": [
     {
       "@type": "Place",
       "additionalType": "country",
       "name": "United States",
       "url": "https://geonames.org/4074035"
     },
     {
       "@type": "Place",
       "additionalType": "state",
       "name": "Washington"
     },
     {
       "@type": "Place",
       "additionalType": "unknown",
       "name": "Snohomish delta"
     },
     {
       "@type": "Place",
       "geo": [
         {
           "@type": "GeoShape",
           "additionalProperty": {
             "@type": "PropertyValue",
             "name": "GeoJSON",
             "value": {
               "type": "FeatureCollection",
               "features": [
                 {
                   "type": "Feature",
                   "properties": {},
                   "geometry": {
                     "type": "Polygon",
                     "coordinates": [
                       [
                         [
                           -122.244873046875,
                           47.936126860169225
                         ],
                         [
                           -122.12265014648438,
                           47.936126860169225
                         ],
                         [
                           -122.12265014648438,
                           48.06385542635001
                         ],
                         [
                           -122.244873046875,
                           48.06385542635001
                         ],
                         [
                           -122.244873046875,
                           47.936126860169225
                         ]
                       ]
                     ]
                   }
                 }
               ]
             }
           }
         },
         {
           "@type": "GeoCoordinates",
           "latitude": 47.99999114325962,
           "longitude": -122.18376159667969
         }
       ]
     }
   ]
 }

}