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Belle Philibosian

The focus of my research is to understand the earthquake cycle, using techniques drawn from the fields of active tectonics and paleoseismology. In various projects I have employed imagery- and LiDAR-based fault mapping, paleoseismic trenching, GPS and InSAR observations, and coral microatoll paleogeodesy.  I pursue the dual goals of scientific understanding and hazard assessment of earthquakes.

EDUCATION

2013    Ph.D. Geology, Division of Geological and Planetary Sciences, California Institute of Technology

2007    M.S. Geological Sciences, Department of Geological Sciences, University of Oregon

2005    B.S. Geology, Division of Geological and Planetary Sciences, California Institute of Technology

                       

EMPLOYMENT

2019–present   Research Geologist, Earthquake Science Center, U.S. Geological Survey

2016–2019       Mendenhall Postdoctoral Research Geologist, Earthquake Science Center, U.S. Geological Survey

2015–2016       Columbia Science Fellow, Columbia University

2013–2015       AXA Postdoctoral Researcher, Equipe de Tectonique, Institut de Physique du Globe de Paris

Science and Products

Photomosaics and logs associated with study of West Napa Fault at Ehlers Lane, north of Saint Helena, California

The West Napa Fault has previously been mapped as extending ~45 kilometers (km) from northern Vallejo to southern Saint Helena, California, dominantly running along the western edge of Napa Valley. A zone of fault strands (some previously unmapped) along a ~15-km section of the fault ruptured during the 2014 magnitude 6.0 South Napa earthquake, illustrating the need for further investigation of th
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Natural Hazards, Earthquake Hazards, Earthquake Science Center, Geosciences and Environmental Change Science Center

20th-century strain accumulation on the Lesser Antilles megathrust based on coral microatolls

The seismic potential of the Lesser Antilles megathrust remains poorly known, despite the potential hazard it poses to numerous island populations and its proximity to the Americas. As it has not produced any large earthquakes in the instrumental era, the megathrust is often assumed to be aseismic. However, historical records of great earthquakes in the 19th century and earlier, which were most li
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Natural Hazards, Earthquake Hazards, Earthquake Science Center

Creep on the Sargent Fault over the past 50 yr from alignment arrays with implications for slip transfer between the Calaveras and San Andreas Faults, California

The 55‐km‐long Sargent fault connects the creeping Calaveras fault with the locked San Andreas fault through the Santa Cruz Mountains west of Gilroy, California. The position of the Sargent fault between these two faults may have implications for slip transfer and strain accumulation between a creeping and locked fault. The detection and measurement of creep on the Sargent fault would indicate whe
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Natural Hazards, Earthquake Hazards, Earthquake Science Center

Documentation of Surface Fault Rupture and Ground‐Deformation Features Produced by the 4 and 5 July 2019 Mw 6.4 and Mw 7.1 Ridgecrest Earthquake Sequence

The MwMw 6.4 and MwMw 7.1 Ridgecrest earthquake sequence occurred on 4 and 5 July 2019 within the eastern California shear zone of southern California. Both events produced extensive surface faulting and ground deformation within Indian Wells Valley and Searles Valley. In the weeks following the earthquakes, more than six dozen scientists from government, academia, and the private sector carefully
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Natural Hazards, Earthquake Hazards, Earthquake Science Center

Evidence of previous faulting along the 2019 Ridgecrest, California earthquake ruptures

The July 2019 Ridgecrest earthquake sequence in southeastern California was characterized as surprising because only ~35% of the rupture occurred on previously mapped faults. Employing more detailed inspection of pre-event high-resolution topography and imagery in combination with field observations, we document evidence of active faulting in the landscape along the entire fault system. Scarps, de
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Natural Hazards, Earthquake Hazards, Earthquake Science Center, Geologic Hazards Science Center

Segmentation and supercycles: A catalog of earthquake rupture patterns from the Sumatran Sunda Megathrust and other well-studied faults worldwide

After more than 100 years of earthquake research, earthquake forecasting, which relies on knowledge of past fault rupture patterns, has become the foundation for societal defense against seismic natural disasters. A concept that has come into focus more recently is that rupture segmentation and cyclicity can be complex, and that a characteristic earthquake model is too simple to adequately describ
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Natural Hazards, Earthquake Hazards, Earthquake Science Center

Surface displacement distributions for the July 2019 Ridgecrest, California earthquake ruptures

Surface rupture in the 2019 Ridgecrest, California, earthquake sequence occurred along two orthogonal cross faults and includes dominantly left‐lateral and northeast‐striking rupture in the Mw 6.4 foreshock and dominantly right‐lateral and northwest‐striking rupture in the Mw 7.1 mainshock. We present >650 field‐based, surface‐displacement observations for these ruptures and synthesize our results
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Natural Hazards, Earthquake Hazards, Earthquake Science Center, Geologic Hazards Science Center, Geology, Minerals, Energy, and Geophysics Science Center

Coupling of Indo-Pacific climate variability over the last millennium

The Indian Ocean Dipole (IOD) impacts climate and rainfall across the world, and most severely in nations surrounding the Indian Ocean1-4. The frequency and intensity of positive IOD events increased during the 20th Century5 and may continue to intensify in a warming world6; however, confidence in future IOD changes is limited by known biases in model representations of the IOD7 and the lack of in
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Natural Hazards, Earthquake Hazards, Earthquake Science Center

San Andreas fault earthquake chronology and Lake Cahuilla history at Coachella, California

The southernmost ~100 km of the San Andreas fault has not ruptured historically. It is imperative to determine its rupture history to better predict its future behavior. This paleoseismic investigation in Coachella, California, establishes a chronology of at least five and up to seven major earthquakes during the past ~1100 yr. This chronology yields a range of average recurrence intervals between
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Natural Hazards, Earthquake Hazards, Earthquake Science Center

Photomosaics and Logs of Trenches on the San Andreas Fault near Coachella, California

Valley in southern California east of Dillon Road and south of Avenue 44. Three benched trenches, a total of more than 950 m, were excavated across the fault zone as part of an Alquist-Priolo fault investigation study. These trenches exposed a thick section of latest Holocene lacustrine, fluvial, and shoreline deposits. Only the central and eastern trenches exposed faulting so we confined our inve

Pre-USGS Publications

Philibosian, B., K. Sieh, J.-P. Avouac, D. H. Natawidjaja, H.-W. Chiang, C.-C. Wu, C.-C. Shen, M. R. Daryono, H. Perfettini, B. W. Suwargadi, Y. Lu, and X. Wang (2017). Earthquake supercycles of the Mentawai segment of the Sunda Megathrust in the 17th century and earlier, Journal of Geophysical Research 122, doi:10.1002/2016JB013560.
Philibosian, B., K. Sieh, J.-P. Avouac, D. H. Natawidjaja, H.-W. Chiang, C.-C. Wu, H. Perfettini, C.-C. Shen, M. R. Daryono, and B. W. Suwargadi (2014). Rupture and variable coupling behavior of the Mentawai segment of the Sunda megathrust during the supercycle culmination of 1797 to 1833, Journal of Geophysical Research 119, doi: 10.1002/2014JB011200.
Philibosian, B., K. Sieh, D.H. Natawidjaja, H.-W. Chiang, C.-C. Shen, B.W. Suwargadi, E.M. Hill, and R.L. Edwards (2012). An ancient shallow slip event on the Mentawai segment of the Sunda Megathrust, Sumatra. Journal of Geophysical Research 117, B05401, doi:10.1029/2011JB009075.
Philibosian, B., and M. Simons (2011). A survey of volcanic deformation on Java using ALOS PALSAR interferometric time series. Geochemistry, Geophysics, Geosystems 12, Q11004, doi:10.1029/2011GC003775.
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Locations at Which Paleoseismological Studies Have Been Completed Along Principal Faults in the San Francisco Bay Area

Earthquake Geology and Paleoseismology

USGS scientists study active fault zones by mapping faults, excavating trenches, studying landforms offset by earthquakes, and measuring past and current motion of active faults using alignment arrays, global positioning systems (GPS), and airborne, terrestrial and mobile laser scanning technology. By excavating trenches across active faults, USGS geologists and collaborators are unraveling the...
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Natural Hazards, Earthquake Hazards
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Earthquake Geology and Paleoseismology

USGS scientists study active fault zones by mapping faults, excavating trenches, studying landforms offset by earthquakes, and measuring past and current motion of active faults using alignment arrays, global positioning systems (GPS), and airborne, terrestrial and mobile laser scanning technology. By excavating trenches across active faults, USGS geologists and collaborators are unraveling the...
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Lidar point cloud, GNSS, and raster data from near St. Helena, CA, March 30 and August 1, 2017

Text files: These data are text files of GNSS survey points collected along a trace of the West Napa Fault Zone near Ehler?s Lane north of St. Helena, California. Data were collected to aid in paleoseismic investigation of the suspected fault strand and to characterize local geomorphology. Data were collected on March 31, and August 1, 2017 using a Leica Viva GS15 survey grade GPS. The data are de
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Earthquake Hazards

Pre-existing features associated with active faulting in the vicinity of the 2019 Ridgecrest, California earthquake sequence

This dataset is composed of linear active tectonic and other relevant features (scarps, deflected drainages, and lineaments and contrasts in topography, vegetation, and ground color) mapped based on high-resolution topography, aerial/satellite imagery, and field observations. The mapping covers the area surrounding the 2019 Ridgecrest, California earthquake surface ruptures. Point locations of fie
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Earthquake Hazards

2017b high resolution seismic imaging of the West Napa Fault Zone, St. Helena, California

In September 2017, the U.S. Geological Survey acquired high resolution P- and S-wave seismic data across the suspected trace of the West Napa Fault zone in St. Helena, California, approximately 70 m north of the previous seismic survey conducted in April 2017 (Chan et al., 2018). We acquired seismic reflection, refraction, and guided-wave data along a 75-m-long profile across the expected trend of

2017 seismic imaging of the West Napa Fault Zone, St. Helena, California

In April 2017, the U.S. Geological Survey acquired high resolution P- and S-wave seismic data across the suspected trace of the West Napa Fault zone in St. Helena, California. We acquired seismic reflection, refraction, and guided-wave data along a 215-m-long profile across the expected trend of the West Napa Fault zone. To acquire the reflection and refraction data, we co-located shots and geopho

Science and Products