Earthquake Science Center Seminars podcast

#Science #Government #Seismology #Hazards #Tectonics #Seminar #USGS, Menlo Park (Scott Haefner #Video #Natural Sciences #Podcasting Education #USGS #Earthquakes #Prepared #Tsunamis

28:24

In our second installment of the Small Business Starter Kit series - we’re tackling a topic that’s sometimes tricky, sometimes confusing, but ever-present: taxes. Hosts Austin and Jannese have an insightful conversation with entrepreneur Isabella Rosal who started 7th Sky Ventures , an exporter and distributor of craft spirits, beer, and wine. Having lived and worked in two different countries and started a company in a heavily-regulated field, Isabella is no stranger to navigating the paperwork-laden and jargon-infused maze of properly understanding taxes for a newly formed small business. Join us as she shares her story and provides valuable insight into how to tackle your business’ taxes - so they don’t tackle you. Learn more about how QuickBooks can help you grow your business: QuickBooks.com See omnystudio.com/listener for privacy information.…

Earthquake Science Center Seminars

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Open dialogue about important issues in earthquake science presented by Center scientists, visitors, and invitees.

20 episoade

Earthquake Science Center Seminars

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updated acum 19 zile

Distribuie

Pagina seriei•Feed

Open dialogue about important issues in earthquake science presented by Center scientists, visitors, and invitees.

20 episoade

#Science #Government #Seismology #Hazards #Tectonics #Seminar #USGS, Menlo Park (Scott Haefner #Video #Natural Sciences #Podcasting Education #USGS #Earthquakes #Prepared #Tsunamis

Toate episoadele

Earthquake Science Center Seminars

1
Investigating seismic hazard across timescales using field methods and numerical modeling 1:00:00

acum 19 zile1:00:00

1:00:00

Betsy Madden, San Jose State University Seismic hazard assessments currently depend on fault slip rates, the cumulative offset over many earthquakes along individual faults, to determine the probability of earthquakes of a certain magnitude over a certain time period and potential ground motions. Geologic fault slip rates are estimated by a combination of field and laboratory techniques. Such data can be generated synthetically with mechanical models that capture slip rate variations along complex, three-dimensional fault networks. I will discuss opportunities provided by these synthetic data, as well as integration of the results with dynamic rupture models of individual earthquakes.…

Earthquake Science Center Seminars

1
Imaging Big Things at Fine Scales with Fiber-Measured Earthquake Wavefields 1:00:00

acum 5 weeks1:00:00

1:00:00

James Atterholt, USGS Observations of broad-scale lithospheric structure and large earthquakes are often made with sparse measurements and are low resolution. This makes interpretations of the processes that shape the lithosphere fuzzy and nonunique. Distributed Acoustic Sensing (DAS) is an emergent technique that transforms fiber-optic cables into ultra-dense arrays of strainmeters, yielding meter-scale resolution over tens of kilometers for long recording periods. Recently, new techniques have made probing fiber-measured earthquake wavefields for signatures of large-scale deformation and dynamic behavior possible. With fibers in the Eastern California Shear Zone and near the Mendocino Triple Junction, I use DAS arrays to measure a diversity of tectonic-scale phenomena. These include the length scale over which the Garlock Fault penetrates the mantle, the plumbing system of the Coso Volcanic Field at the crust-mantle boundary, the topographic roughness of the Cascadia Megathrust, and the time-dependent rupture velocity of the 2024 M7 Cape Mendocino earthquake. Dense measurements vastly improve the clarity with which we can view these processes, offering new insights into how the lithosphere evolves and what drives the behavior of large earthquakes.…

Earthquake Science Center Seminars

1
Friction and faulting in heterogeneous systems 1:00:00

acum 6 weeks1:00:00

1:00:00

Doron Morad, University of California, Santa Cruz In natural fault surfaces, stresses are not evenly distributed due to variations in the contact population within the medium, causing frictional variations that are not easy to anticipate. These variations are crucial for understanding the kinematics and dynamics of frictional motion and can be attributed to both the intact material and granular media accommodating the principal slip zone. Here, I explore the effects of heterogeneous frictional environments using two different approaches: fracture dynamics on non-mobilized surfaces and granular systems on mobilized ones. First, I will present a quantitative analysis of laboratory earthquakes on heterogeneous surfaces, incorporating both laboratory-scale seismic measurements coupled with high-speed imaging of the controlled dynamic ruptures that generated them. We generated variations in the rupture properties by imposing sequences of controlled artificial barriers along the laboratory fault. We first demonstrate that direct measurements of imaged slip events correspond to established seismic analysis of acoustic signals; the seismograms correctly record the rupture moments and maximum moment rates. We then investigate the ruptures’ early growth by comparing their measured seismogram velocities to their final size. We investigate the laboratory conditions that allow final size predictability during the rupture early growth. Due to higher initial elastic energies imposed prior to nucleation, larger events accelerate more rapidly at the rupture onset for both heterogeneous and non-heterogeneous surfaces. Second, I present a new Couette-style deformation cell designed to study stress localization in two-dimensional granular media under different flow regimes. This apparatus enables arbitrarily large deformations and spans four orders of magnitude in driving velocity, from sub-millimeter to meters per second. Using photoelasticity, we measure force distribution and localization within the granular medium. High-speed imaging captures data from a representative patch, including both lower and upper boundaries, allowing us to characterize local variations in stress and velocity. For the first time, we present experimental results demonstrating predictive local granular behavior based on particle velocities, velocity fluctuations, and friction, as defined by [tau/sigma_n]. Our findings also reveal that stress patterns in the granular medium are velocity-dependent, with higher driving velocities leading to increased stress localization. These two end-member cases of frictional sliding, one dominated by gouge, and the second by intact surfaces, highlight two fundamental aspects of friction dynamics. The spatial distribution of heterogeneity directly influences stress distribution and, consequently, the stability of the medium. With these experimental methods, we can now measure and even control these effects.…

Earthquake Science Center Seminars

1
Leveraging high temporal and spatial resolution geodetic data through the earthquake cycle 1:00:00

acum 7 weeks1:00:00

1:00:00

Cassie Hanagan, USGS Advancing our understanding of earthquake processes inevitably pushes the bounds of data resolution in the spatial and temporal domains. This talk will step through a series of examples leveraging two relatively niche geodetic datasets for understanding portions of the earthquake cycle: (1) temporally dense and sensitive borehole strainmeter (BSM) data, and (2) spatially dense sub-pixel image correlation displacement data. More specifically, I will detail gap-filling benefits of these two datasets for different earthquakes. BSMs respond to a frequency of deformation that bridges the capabilities of more common GNSS stations and seismometers. As such, they are typically installed to capture deformation signals such as slow slip or transient creep. In practice they are also useful for measuring dynamic and static coseismic strains. This portion of the talk will focus on enhanced network capabilities for detecting both coseismic and postseismic deformation with a relatively new BSM array in the extensional Apennines of Italy, with events spanning tens to thousands of kms away. Then, we will transition toward how these instruments can constrain spatiotemporally variable afterslip following the 2019 Mw7.1 Ridgecrest, California earthquake. High spatial resolution displacements from sub-pixel image correlation serve as gap-filling datasets in another way – providing higher spatial resolution (~0.5 m) maps of the displacement fields than any other method to date, and patching areas where other methods fail to capture the full deformation magnitude or extent, such as where InSAR decorrelates. This portion of the talk will focus on new results that define expected displacement detection thresholds from high-resolution satellite optical imagery and, alternatively, from repeat lidar data. Examples will include synthetic and real case studies of discrete and diffuse deformation from earthquakes and fault creep.…

Earthquake Science Center Seminars

1
Northern California 3D seismic velocity models and earthquake ground motion simulations 1:00:00

acum 10 weeks1:00:00

1:00:00

Evan Hirakawa, USGS Northern California, specifically the San Francisco Bay Area, is a great place to study earthquake hazards and risk, due to its dense population centers surrounded by active faults, as well as complex geology that strongly influences earthquake ground motions. Computer simulations of seismic wave propagation which can incorporate 3D models of the subsurface properties and complex faulting behavior are good tools for studying seismic hazard, but ultimately require more development before unlocking full potential; specifically, the 3D seismic velocity models need to be further developed in many places and the simulated motions need to be validated with real, recorded data. In this talk, I will summarize a few different research projects on these topics. First I will review recent efforts to improve the USGS San Francisco Bay region 3D seismic velocity model (SFCVM), the leading community velocity model in the area, and describe some of its interesting features. This will be followed by a preview of ongoing work from collaborators and some other promising avenues to explore, in hopes of further improving the model and stoking more community involvement. In the second part of the talk, I will switch gears and move farther north, to the Humboldt County area, where a recent M7 earthquake occurred offshore. I will show some preliminary modeling results, discuss the datasets available from this event, and describe some of the local geology and efforts to better understand subsurface structure.…

Earthquake Science Center Seminars

1
Engineering modeling for assessing and optimizing seismic resilience 1:00:00

acum 19 weeks1:00:00

1:00:00

Omar Issa, ResiQuant (Co-Founder)/Stanford University A study by FEMA suggests that 20-40% modern code-conforming buildings would be unfit for re-occupancy following a major earthquake (taking months or years to repair) and 15-20% would be rendered irreparable. The increasing human and economic exposure in seismically active regions emphasize the urgent need to bridge the gap between national seismic design provisions (which do not consider time to recovery) and community resilience goals. Recovery-based design has emerged as a new paradigm to address this gap by explicitly designing buildings to regain their basic intended functions within an acceptable time following an earthquake. This shift is driven by the recognition that minimizing downtime is critical for supporting community resilience and reducing the socioeconomic impacts of earthquakes. This seminar presents engineering modeling frameworks and methods to support scalable assessment and optimization of recovery-based design, including: 1. Procedures for selection and evaluation of recovery-based performance objectives and study the efficacy of user-defined checking procedures. 2. A framework to rapidly optimize recovery-based design strategies based on user-defined performance objectives. 3. Building technology to support utilization of these approaches across geographies and industrial verticals. Together, these contributions provide the technical underpinnings and industry-facing data requirements to perform broad, national-scale benefit-cost analysis (BCA) studies that can accelerate decision-making and engineering intuition as resilient design progresses in the coming years.…

Earthquake Science Center Seminars

1
DAS for EEW: what about the dynamic range? 1:00:00

acum 24 weeks1:00:00

1:00:00

Martijn van den Ende, Université Côte d'Azur Already for several years it has been suggested that Distributed Acoustic Sensing (DAS) could be a convenient, low-cost solution for Earthquake Early Warning (EEW). Several studies have investigated the potential of DAS in this context, and demonstrated their methods using small local earthquakes. Unfortunately, DAS has a finite dynamic range that is easily exceeded in the near-field of large earthquakes, which severely hampers any EEW efforts. In this talk, I will present a detailed analysis of the dynamic range, and how it impacts EEW: where does it come from? What can we do when the dynamic range is exceeded? And is there still hope for DAS-based EEW systems?…

Earthquake Science Center Seminars

1
The mechanics of (laboratory) earthquakes and aseismic slip due to fluid injection 1:00:00

acum 25 weeks1:00:00

1:00:00

Sara Beth Cebry, U.S.G.S. luid injection decreases effective normal stress on faults and can stimulate seismicity far from active tectonic regions. Based on earthquake nucleation models and measured stress levels, slip will be stable, aseismic, and limited to the fluid pressurized region—contrary to observed increases in seismicity. To understand how fluid injection effects earthquake initiation, rupture, and termination, I used large-scale laboratory faults to experimentally link effects of direct fluid injection to rupture behavior. Comparison between the nucleation of dynamic events with and without fluid pressure showed that rapid fluid injection into a low permeability fault increases multi-scale stress/strength heterogeneities that can initiate seismic slip. Factors that increase the intensity of the heterogeneity, such as increased injection rate or background normal stress, promote the initiation of small seismic events that have the potential to “run away” and propagate beyond the fluid pressurized region. Whether or not the seismic slip can “run away” depends on the background shear stress levels. When the fault was near critically stressed, dynamic slip initiated quickly after high fluid pressure levels were reached. The dynamic slip event propagated far beyond the fluid pressurized region. In comparison, when the fault was far from critically stressed, dynamic slip initiated hundreds of seconds after high injection pressures were reached and this event was limited in size by the region affected by fluid pressure. We conclude that localized decreases in effective normal stress due to fluid pressure can initiate slip, sometimes seismic slip, but the background shear stress controls whether or not that slip and grows into a large earthquake.…

Earthquake Science Center Seminars

1
Rapid, physics-informed seismic wavefield predictions using high-performance computing and reduced-order modeling techniques 1:00:00

acum 26 weeks1:00:00

1:00:00

John Rekoske, University of California San Diego Rapidly estimating the ground shaking produced by earthquakes in real-time, and from future earthquakes, are important challenges in seismology. Numerical simulations of seismic wave propagation can be used to estimate ground motion; however, they require large amounts of computing power and are too slow for real-time problems, even with modern supercomputers. Our aim is to develop a method using both high-performance computing and machine learning techniques to obtain a close approximation of simulated seismic wavefields that can be solved rapidly. This approach integrates physics into the source- and site-specific ground motion estimates used for real-time applications (e.g., earthquake early warning) as well as many-source problems (e.g., probabilistic seismic hazard analysis). Specifically, I will focus this talk on applying data-driven reduced-order models (ROMs) that are based on the interpolated proper orthogonal decomposition method. I will discuss our work using ROMs to (1) instantaneously generate peak ground velocity maps and (2) to rapidly generate three-component velocity seismograms for earthquakes in the greater Los Angeles area. The approach is flexible, in that it can generate 3D elastodynamic Green’s functions which we can use to simulate seismograms for complex kinematic earthquake rupture models. Lastly, I will show how this approach can provide accurate, near-real-time wavefields that could be used to rapidly inform about possible earthquake damage.…

Earthquake Science Center Seminars

1
Source, path, and site effects and their role on earthquake ground motions 1:00:00

acum 29 weeks1:00:00