Geology topics

Ginevra Moore

Publications and source records attributed to Ginevra Moore.

4 recordsLinked to original sources

USGS2026

Deformed submarine terraces in Puget Sound, Pacific Northwest, indicate only one M >~7.5 earthquake on the Seattle fault zone in the past 11,000 yr

Submerged marine terraces in Puget Sound, deformed across the Seattle fault zone (SFZ), indicate that only one earthquake as large as M~7.5 has occurred in at least the past 11 kyr. Previous paleoseismic studies document a M~7.5 earthquake between 923–4 CE, which uplifted coastal marine terraces by as much as 8 m. We demonstrate that this earthquake was the only such event since ~11 ka by mapping and quantifying deformation of older marine terraces, now submerged in Puget Sound. The submerged terraces, attributed to a late-glacial sea-level lowstand, record both glacial isostatic rebound and tectonic deformation. Vertical offset of the ~11 ka terraces within the SFZ is comparable to that of the marine terraces uplifted in 923 CE, implying no additional large (M>~7.5) earthquake on the SFZ since ~11 ka. This result implies a longer recurrence interval than current hazard estimates, which assumes recurrence of M>7.1 events every 5 kyr. Our mapping of SFZ deformation since ~11 ka also supports fault segmentation and contiguous block uplift between the Seattle and Tacoma fault zones.

Washington↗

USGS2020

The Alaska Amphibious Community Seismic Experiment

The Alaska Amphibious Community Seismic Experiment (AACSE) is a shoreline‐crossing passive‐ and active‐source seismic experiment that took place from May 2018 through August 2019 along an ∼ 700    km "> ∼ 700 km ∼700 km long section of the Aleutian subduction zone spanning Kodiak Island and the Alaska Peninsula. The experiment featured 105 broadband seismometers; 30 were deployed onshore, and 75 were deployed offshore in Ocean Bottom Seismometer (OBS) packages. Additional strong‐motion instruments were also deployed at six onshore seismic sites. Offshore OBS stretched from the outer rise across the trench to the shelf. OBSs in shallow water ( ⁠ < 262    m "> < 262 m <262 m depth) were deployed with a trawl‐resistant shield, and deeper OBSs were unshielded. Additionally, a number of OBS‐mounted strong‐motion instruments, differential and absolute pressure gauges, hydrophones, and temperature and salinity sensors were deployed. OBSs were deployed on two cruises of the R/V Sikuliaq in May and July 2018 and retrieved on two cruises aboard the R/V Sikuliaq and R/V Langseth in August–September 2019. A complementary 398‐instrument nodal seismometer array was deployed on Kodiak Island for four weeks in May–June 2019, and an active‐source seismic survey on the R/V Langseth was arranged in June 2019 to shoot into the AACSE broadband network and the nodes. Additional underway data from cruises include seafloor bathymetry and sub‐bottom profiles, with extra data collected near the rupture zone of the 2018 M w "> M w Mw 7.9 offshore‐Kodiak earthquake. The AACSE network was deployed simultaneously with the EarthScope Transportable Array (TA) in Alaska, effectively densifying and extending the TA offshore in the region of the Alaska Peninsula. AACSE is a community experiment, and all data were made available publicly as soon as feasible in appropriate repositories.

Alaska↗

USGS2018

Slab2, a comprehensive subduction zone geometry model

Subduction zones are home to the most seismically active faults on the planet. The shallow megathrust interfaces of subduction zones host our largest earthquakes and are likely the only faults capable of magnitude 9+ ruptures. Despite these facts, our knowledge of subduction zone geometry—which likely plays a key role in determining the spatial extent and ultimately the size of subduction zone earthquakes—is incomplete. We calculated the three-dimensional geometries of all seismically active global subduction zones. The resulting model, called Slab2, provides a uniform geometrical analysis of all currently subducting slabs.

Science↗

USGS2017

2017 Valparaíso earthquake sequence and the megathrust patchwork of central Chile

In April 2017, a sequence of earthquakes offshore Valparaíso, Chile, raised concerns of a potential megathrust earthquake in the near future. The largest event in the 2017 sequence was a M 6.9 on 24 April, seemingly colocated with the last great-sized earthquake in the region—a M 8.0 in March 1985. The history of large earthquakes in this region shows significant variation in rupture size and extent, typically highlighted by a juxtaposition of large ruptures interspersed with smaller magnitude sequences. We show that the 2017 sequence ruptured an area between the two main slip patches during the 1985 earthquake, rerupturing a patch that had previously slipped during the October 1973 M 6.5 earthquake sequence. A significant gap in historic ruptures exists directly to the south of the 2017 sequence, with large enough moment deficit to host a great-sized earthquake in the near future, if it is locked.

Valparaiso↗