During earthquakes along the subduction zone, the ground deforms vertically and the ground shakes as seismic waves propagate through the Earth. This vertical deformation can place marsh deposits, once partly above tide where plants can grow, lower into the tidal zone where plants may not grow. The marsh deposits then get buried by mud. Biological microfossils found in the sediment can be used to infer the relative vertical position of the ground when the sediment was deposited. The ground shaking also triggers submarine landslides that leave deposits along the seafloor. Radiocarbon ages are used to constrain the timing of deposition for sediments in both onshore and offshore sedimentary settings. Figure 1. The CSZ fault is designated by a red line with triangles. Relative plate motions are shown as black arrows and the rates are labeled in mm/year. From McCrory et al. (2006). Methods: Geologists placed sediment cores along the coast in bays and estuaries along the entire subduction zone (Atwater et al., 2005; Nelson et al., 2006). These cores were placed to find buried marsh deposits. Microfossils are used in the marsh cores to interpret the sedimentary environment of the sediments that were deposited. Geologists also placed sediment cores in the deep sea offshore of the CSZ (Goldfinger et al., 2012). These cores were placed to find deposits of submarine landslides possibly triggered by earthquakes on the CSZ. Organic material is used for radiocarbon age control based on the radioactive half-life of 14C for both types of studies.
During earthquakes along the subduction zone, the ground deforms vertically and the ground shakes as seismic waves propagate through the Earth. This vertical deformation can place marsh deposits, once partly above tide where plants can grow, lower into the tidal zone where plants may not grow. The marsh deposits then get buried by mud. Biological microfossils found in the sediment can be used to infer the relative vertical position of the ground when the sediment was deposited. The ground shaking also triggers submarine landslides that leave deposits along the seafloor. Radiocarbon ages are used to constrain the timing of deposition for sediments in both onshore and offshore sedimentary settings. Figure 1. The CSZ fault is designated by a red line with triangles. Relative plate motions are shown as black arrows and the rates are labeled in mm/year. From McCrory et al. (2006). Methods: Geologists placed sediment cores along the coast in bays and estuaries along the entire subduction zone (Atwater et al., 2005; Nelson et al., 2006). These cores were placed to find buried marsh deposits. Microfossils are used in the marsh cores to interpret the sedimentary environment of the sediments that were deposited. Geologists also placed sediment cores in the deep sea offshore of the CSZ (Goldfinger et al., 2012). These cores were placed to find deposits of submarine landslides possibly triggered by earthquakes on the CSZ. Organic material is used for radiocarbon age control based on the radioactive half-life of 14C for both types of studies.