Research Projects of Robert W. Clayton

Current Projects

• Los Angeles Basin Structure Using local earthquakes and gravity to determine the basin depth and the shear wave velocities. Plan to use converted waves from earthqakes occuring beneath the basin and recorded on the CSN network. A result for the northern part of the basin from the Ridgecrest Earthquake recorded on the CSN network is given in     Pub2022     Pub2022-supp     Pub2022-movie

• Fourier Neural Operators - UNO (with Zach Ross and Kamyar Azizzadenseshi) Using AI mehtods to replace numeric simulations of wavefields for a much reduced cost. For a particular dimension of model, the Neural Operator is trained with a series of models with random velocities and source locations. The resulting model can be used to determine the full wave solution between arbitrary source and receiver positions and velocity function. Hence, the trained model can be used for all situations where the dimenionality fits. Also since the model is meshless the solution can be upscaled. We have done with the 2D acoustic equation - Pub2021 the 2D elastic wave equation - Pub2023 , and the 3D elastic using the Helmhotz equation Pub2024 . Currently we are applying this to a real data example.

• Near-Surface Los Angeles Basin. Oil industry data from Long Beach, Seal Beach, Rosecrans and Santa Fe Springs surveys are cross-correlated with the permanent SCSN broadband network in the Los Angles area to produce surface wave coverage in the central Los Angeles Basin. These are invrted to determine the shear wave velocities down to about 1 km depth. P-waves 2020     ML-Dispersion 2020     S-waves 2021

• Autocorrelation Reflection Imaging in Long Beach. Autocorrelations generated by stacks of near zero-offset virtual gathers are used to create reflection sections under Long Beach. The results show a Moho dipping at 65-degrees and a laminated lower crust. SEG Abstract     SRL Method Paper     GJI Results Paper

• BASINS - Imaging the San Bernardino, San Gabriel, and Chino Basins in Los Angeles. (with Patricia Persaud - LSU) We are interested in determining the 3D shape of the basins in northern Los Angeles in order to assess their role in channeling energy from earthquakes originating on the southern San Andreas Fault into downtown LA. This involes several 2D profiles across the basins using 3C nodes along with broadband sensors deployed along the SAF and in the basins to determine the 3D structure. The broadband sensors will also allow the virtual earthquake scenarions along the SAF, which will be compared simulation of the ground motions. The project done in collaboration with Patricia Persaud of LSU. The field work was completed in late 2019 with funding from the USGS and SCEC.   Web Page.   LSU-Web Page.     Pub2018     Pub2018-supp     Funded NSF Proposal. We have completed the shape/depth of the basins Pub2023a and thw shear wave velocities within them Pub2023b. We have also done the Receiver Functions Pub2023c.

• Instrumenting Tall Buildings in Los Angeles (with M. Kohler, R. Guy, and T. Heaton)
  We are in the process of placing over 100 CSN sensors (see below) in a 52 story build in downtown Los Angeles. The object is to see if earthquake damage can be detected by comparing the post-earthquake response of the building with the pre-earthquake response. Web Page.     Funded Proposal.     Pub2015     Pub2016     Pub2018     Pub2020

• Long Beach 3D Seismic Network
  In 2011, NodalSeismic Inc. recorded a dense seismic survey in Long Beach, CA, on behalf of Signal Hill Petroleum Inc., in order to better define the Long Beach Oil Field. The network consisted of over 5000 sensors that were deployed in 7 x 10 km area for siz months. The sensors recored continuous data 24-hours a day, make this a unique data set for imaging with ambient noise. More detail and some movies of local earthquakes recorded by the network can be seen at this link.   Pub2013   Pub2013   Pub2015   Pub2016   Pub2018   Pub2020a   Pub2020b   Pub2021
  Work on additional dense surveys is now in progress: Santa_Fe_Springs   Western_Orange_County   Rosecrans   AlmondCrest

• Community Seismic Network (CSN) link
  The seismological Laboratory along with Earthquake Engineering and Computer Science are developing a density seismic network based on low-cost sensors connected through the internet to the Google Apps Engine. The purpose is to provide block-by-block and floor-by-floor measurements of acceration in the event of a significant earthquake.   Pub2011     Pub2015     Pub2016     Pub2020     Pub2020     Pub2021

Past Projects - occassionally revisited

• San Andreas Faults Array
  We deployed 120 nodes along and across the San Andreas Fault in Peachtree Valley, CA (40 km NW if Parkfield) to detetct micro-seismicity. This section of the fault creeping (largely aseismic) and purpose to determine the level of small earthquakes. The project was done inconjuction with the CCSE survey. Web Page.    

• GECO - Geometry of the Cocos Plate (with Xyoli Perez-Campos, UNAM)
  Approximately 10 broadband stations have been deployed around the eastern end of the Trans Mexican Volcanic Belt in two wave from 2013 to 2016. This location is where the Cocos Slab changes from flat to normal dipping, but the geometry of the arc volcanoes indicates this is not a simple transition. This project has been absorbed into the Trans Mexican Volcanic Belt project above. Web Page.   See TMVB above.

• Imaging the Eastern Trans-Mexican Volcanic Belt (TMVB) The eastern end of the TMVB is the transition from flat subduction to normal subduction in central Mexico. How this transition take place is unclear. The slab appears to transition smoothly through the zone, but the sufrace topography (Orizaba to the bottom of the Veracruz Basin) has one of the steepest gradients in the world (12 km relief over 100 km). It is also the location of an apparent slab tear. Web Page.     Funded NSF Proposal.     Pub2018     Pub2018-supp     Pub2019     Pub2019-supp     Funded NSF Proposal.

• Wallowa (with Gene Humphreys, Amanda Thomas of U. of Oregon, and Kirsten Nicolaysen of Whitman College) This project consists of a dense linear survey over the Wallowa Mtns in NE Oregon (the leading point in the Yellowstone hotspot) with the purpose of discerning two models for their origin - volcanic or delamination. The array will consist of broadband sensors with a local section with nodes. The survey started in mid-2016, and ended in May, 2018. Web Page.     Funded NSF Proposal.     Pub2020     Pub2020-supp     Pub2022     Pub2022-supp

• Lost Hills Arrays Two 50-element mini-arrays were place on either sie of the Lost Hills oilfield in the Central Valley, CA with the purpose detecting micro-seismicity. The arrays used Gen2 Fairfield Nodes and were out fron Dec 4, 2015 to Jan 10, 2016 (45 days). Web Page.

• Central California Seismic Experiment (with B. Schmandt of U. New Mexico).
  In the latter half of 2013, we will be installing 35-40 broadband station across central California, from the coast to the Sierran foothills. The purpose of the survey is determine if the Isabella Drip is due to delaination of the Sierran root, or is the downdip extension of the Monterey microplate. Web Page.     Flyer.     NSF-Proposal.     Pub2018a     Pub2018b     Pub2020

• LASSIE (Los Angeles Seismic Syncline Interferometry Experiment) is a dense broadband array across the Los Angeles Basin designed to determine the 2D velocity and structure (basin depth and Moho). It was a low-cost urban deployment (residential backyards) that lasted about 45 days. The experiment was a joint project of Caltech, USGS (E. Cochran), UCLA (R. Davis), CalPoly Pomona (J. Polet), NodalSeismic (D. Hollis, M. Barklage), and California Resources (nee Occidental Petroleum) (B. Andersen). Web Page.
  Pub2016a     Pub2016a-supp     Pub2016b     Pub2016b-supp Pub2020

• Peru Subduction Experiment (PeruSE)   detailed description   data link
  The Caltech Tectonics Observatory and the UCLA CENS's project have deployed 100 broadband senors along three lines in southern Peru to investigate the flat slab subduction. Pub-2012   Pub-2012-supp   Pub-2014   Pub-2013   Pub-2014   Pub-2015   Pub-2015   Pub-2015   Pub-2018

• Analysis of Sonobuoy and MCS data in the Western Ross Sea, Anarctica Examples of the sonobuoy data.
  Based on sonobuoy and multichannel seismic data we recorded during the NBP0701 cruise to the western Ross Sea, we have been devloping a crustal model to address the question of whether the Adare Trough, a spreading center active 40 Ma, extends under the Antarctic continent.   Pub-2010   Pub-2012   Pub-2014

• Meso-America Subduction Project (MASE) detailed description   old link   data link
  This is a cooperative project involving Caltech's Tectonics Observatory, UCLA's CENS, Geophysical Institute at UNAM and the Center for Geosciences at UNAM. The seismic component consisted of 100 broadband seismometers across central Mexico. Flat subduction is observed for the first 250 km from the trench. The array ran from 2005-2007   Pub-2008   Pub-2008   Pub-2009   Pub-2009   Pub-2009   Pub-2010   Pub-2010   Pub-2011   Pub-2012   Pub-2012   Pub-2012   Pub-2013   Pub-2014   Pub-2014

• Veracruz-Oaxaca Seismic Line (VEOX) detailed description   data link
  This experiment is a follow on to the MASE experiment and crosses southern Mexico just north of the Techauntepec Ridge. The slab is dipping at 20 degrees in this region. The array was active from 2007 to 2009.   Pub-2011   Pub-2012   Pub-2012

• NARS-Baja Seismic Array link
  This array is a partnership between Caltech, Utrecht and Cicese and is designed to provided a regional seismic model for the Gulf of California. This region has been undergoing active rifting for the past 6 million years. The array ran from 2002-2008.   Article-2004   Pub-2007   Pub-2014   Pub-2015

• Booming Sand Dunes   link
  Near-surface geophysical methods (seismic and radar) are used to determine the structure of sand dunes in order to explain the phenomena of "booming" that some experience in the summer months.   Pub-2007   Comment-2007   Reply-2008   Pub-2012   Pub-2015

• Southern California Earthquake Data Center (SCEDC) official link
  I am the principle investigator for this project that is the distribution point for seismic data recorded by the Southern California Seismic Network.   Pub-2021

• Ocean Microseisms
  We are investigating the generation of ocean microseisms by looking at their seismic response. Pub-2008

• Crustal/Upper-Mantle Structure of New Zealand link
  We are building a crust and upper mantle model for the South Island of New Zealand. To date, we have completed and crustal model based on receiver functions.   Pub-2008

• Representation Method for Velocity/Structure Models
  We are investigating an alternative format for representing regional models that uses the properties defined in vertical columns. zthe advantage of this representaion is that columns can be easily added to removed in the model and it can be easily joined to adjacent models.

• Receiver Functions From Southern California link
  We have produced a set of receiver functions for the broadband stations of the SCSN. The results are presented in two paper and show that there is significant short-wavelength topography on the Moho, which brings into question the popular model of a weak duciile lower crust. Pub-2007   Pub-2007  

• Crustal Q - Scattering or Intrinsic
  Pub-2007

• Tectonics of Western Pacific.
    Pub-2007   Pub-2007   Correction-2007   Pub-2008

• Finite-Diffrence Wave Propagation
    Pub-2014

Past Land Surveys

• San Fernando Valley Node Survey 2023 map
• Los Angeles Basin Node Array 2022 map
• San Gabrial and San Bernardino Node Surveys 2017-2019 map
• Wallowa, Oregon map
• Central California Seismic Experiment (CCSE) map
• LASSIE, Los Angeles map
• Peru map
• MASE and VEOX, Mexico map
• LARSE I and II map
• Southern Sierra Continental Dynamics map
• Calcrust

Marine Cruises

• EW9415 , Southern California Borderland map
• KIWI12, Revelle, 1998 , Manihiki Plateau, W. Pacific small-map   track-map   group-photo Participants track-map
• NBP0102 , Capetown South Africa to Puenta Arenas, Chile map1 map2
• NBP0207 , California to New Zealand map1
• NBP0209 , Ross Sea, Antarctica
• NBP0403c , Hawaii to New Zealand map
• NBP0607C , Lyttleton, NZ to Chatham Islands, NZ map
• NBP0701 , Ross Sea, Antarctica map