Eric M. Thompson
Grace A. Parker
Robert Graves
Kenneth W. Hudnut
Jason Patton
Timothy E. Dawson
Tyler C. Ladinsky
Michael Oskin
Krittanon Sirorattanakul
Kelly Blake
Annemarie S. Baltay
Elizabeth S. Cochran
Susan E. Hough
2020
<p><span>The 2019 Ridgecrest, California, earthquake sequence, including an </span><span class="inline-formula no-formula-id">Mw</span><span> 6.4 event on 4 July and an </span><span class="inline-formula no-formula-id">Mw</span><span> 7.1 approximately 34 hr later, was recorded by 15 instruments within 55 km nearest‐fault distance. To characterize and explore near‐field ground motions from the </span><span class="inline-formula no-formula-id">Mw</span><span> 6.4 foreshock and </span><span class="inline-formula no-formula-id">Mw</span><span> 7.1 mainshock, we augment these records with available macroseismic information, including conventional intensities and displaced rocks. We conclude that near‐field shaking intensities were generally below modified Mercalli intensity 9, with concentrations of locally high values toward the northern and southern termini of the mainshock rupture. We further show that, relative to near‐field ground motions at hard‐rock sites, instrumental ground motions at alluvial near‐field sites for both the </span><span class="inline-formula no-formula-id">Mw</span><span> 6.4 foreshock and </span><span class="inline-formula no-formula-id">Mw</span><span> 7.1 mainshock were depleted in energy at frequencies higher than 2–3 Hz, as expected from ground‐motion models. Both the macroseismic and instrumental observations suggest that sediments in the Indian Wells Valley experienced a pervasively nonlinear response, which helps explain why shaking intensities and damage in the closest population center, Ridgecrest, were relatively modest given its proximity to the earthquakes.</span></p>
application/pdf
10.1785/0220190279
en
Seismological Society of America
Near-field ground motions from the July, 2019 Ridgecrest, California, earthquake sequence
article