Incorporated Research Institutions For Seismology Research Articles

Enriching the GEOFON seismic catalog with automatic energy magnitude estimations

Abstract. We present a seismic catalog (Bindi et al., 2024, https://doi.org/10.5880/GFZ.2.6.2023.010) including energy magnitude Me estimated from P waves recorded at teleseismic distances in the range 20°≤Δ≤98° and for depths shorter than 80 km. The catalog is built starting from the event catalog disseminated by GEOFON (GEOFOrschungsNetz), considering 6349 earthquakes with moment magnitude Mw≥5 occurring between 2011 and 2023. Magnitudes are computed using 1 031 396 freely available waveforms archived in EIDA (European Integrated Data Archive) and IRIS (Incorporated Research Institutions for Seismology) repositories, retrieved through the standard International Federation of Digital Seismograph Networks (FDSN) web services (https://www.fdsn.org/webservices/, last access: March 2024). A reduced, high-quality catalog for events with Mw≥5.8 and from which stations and events with only few recordings were removed forms the basis of a detailed analysis of the residuals of individual station measurements, which are decomposed into station- and event-specific terms and a term accounting for remaining variability. The derived Me values are compared to Mw computed by GEOFON and with the Me values calculated by IRIS. Software and tools developed for downloading and processing waveforms for bulk analysis and an add-on for SeisComP for real-time assessment of Me in a monitoring context are also provided alongside the catalog. The SeisComP add-on has been part of the GEOFON routine processing since December 2021 to compute and disseminate Me for major events via the existing services.

Advancing Geophysics: IRIS and UNAVCO Merge to Form EarthScope Consortium

AbstractA new organization, EarthScope Consortium, was formed 1 January 2023 following the merger of the Incorporated Research Institutions for Seismology (IRIS) and UNAVCO. EarthScope Consortium is a consortium dedicated to supporting transformative global geophysical research and education.

Correlations between the Topography-Induced Gravity, Terrain Structure and the Seismicity in the Gulf of Panama

This study presents new maps of the topographic and geophysical setting and seismicity in the region of the Gulf of Panama. The spatial analysis is based on the comparative analysis of the datasets on geoid, free-air gravity anomaly, topography and earthquakes. The cartographic framework is developed using the Generic Mapping Tools (GMT) scripting toolset. Seismic activity in the Central America is high due to the complex geologic setting, tectonic activity and lithosphere plate subduction. The data include the Earth Gravitational Model (EGM2008), the General Bathymetric Chart of the Oceans (GEBCO) and gravity grids. The seismicity data were collected from the Incorporated Research Institutions for Seismology (IRIS) catalogue on 1970–2021. The variations in data were compared to analyse correlations between the geophysical, seismic and topographic parameters. Free-air gravity, geoid and topographic data derived from the high-resolution datasets were used to investigate their effects on the main seismic sources in the region. The comparison of the maps showed that the distribution of the shallow earthquakes in the Pacific segment of Panama coincides with negative free-air anomalies and lower geoid values. The results revealed high values of geoid in the high mountainous regions of Panama (Cordilliera de Talamanca, southern coast of Peninsula de Azuero and eastern Panama, 77.5–78.5°W), which correspond to the topographic roughness in the highlands. Negative values of geoid are found over the Caribbean Sea basin (−4 to 0 m). The analyses of seismicity showed 1740 earthquake events varying by magnitudes from 2.9 to 7.8 at the depths up to 225 m (near the west coast of Colombia). A high concentration of the earthquakes is in the western region of the Panama’s shelf waters (~82–83.5°W), and on the border with Colombia (~77–78.5°W). High gravity anomalies (over 220 mGal) are found in the mountainous regions which match the geodynamic processes associated with the Earth structure and geodetic and geophysical effects. The regions of the high seismicity were defined in the Gulf of Chiriqui and eastern part of the Gulf of Panama.

Utilization of Seismic Data as a Tsunami Vulnerability Review

This study aimed to analyze seismic data, which is then made into an infographic to map the level of tsunami hazard in the Sikka District. The research was carried out in Sikka District, East Nusa Tenggara, located between 121°55'40''-122°41'30'' east longitude and 08°22'-08°50' south latitude. The data source comes from the IRIS Earthquake Browser, and the analysis stage was carried out in two phases. The first analysis used seismic data analysis, and EQ Energy used IRIS (Incorporated Research Institutions for Seismology) data. Meanwhile, the second analysis maps the tsunami risk by determining the tsunami hazard in areas with the potential for a tsunami. Based on the analysis of seismicity data showed that Sikka District has the potential for an earthquake accompanied by a tsunami. In contrast, the results of the EQ Energy analysis caused by the December 14, 2021 earthquake were known as the value of Ehf = 6.46 × 1014 J and EBB = 5.48 × 1015 J. The analysis of the level of tsunami susceptibility based on the tsunami run-up height in Sikka District showed that the northern coastal area of ​​Flores had various potentials, where the highest vulnerability level was in the Alok subdistrict and parts of Talibura. Meanwhile, the area with the lowest potential was the Kewapante subdistrict.

Exploring TikTok as a promising platform for geoscience communication

Abstract. With TikTok emerging as one of the most popular social media platforms, there is significant potential for science communicators to capitalize on this success and to share their science with a broad, engaged audience. While videos of chemistry and physics experiments are prominent among educational science content on TikTok, videos related to the geosciences are comparatively lacking, as is an analysis of what types of geoscience videos perform well on TikTok. To increase the visibility of the geosciences and geophysics on TikTok and to determine best strategies for geoscience communication on the app, we created a TikTok account called “Terra Explore” (@TerraExplore). The Terra Explore account is a joint effort between science communication specialists at UNAVCO, IRIS (Incorporated Research Institutions for Seismology), and OpenTopography. We produced 48 educational geoscience videos over a 4-month period between October 2021 and February 2022. We evaluated the performance of each video based on its reach, engagement, and average view duration to determine the qualities of a successful video. Our video topics primarily focused on seismology, earthquakes, topography, lidar (light detection and ranging), and GPS (Global Positioning System), in alignment with our organizational missions. Over this time period, our videos garnered over 2 million total views, and our account gained over 12 000 followers. The videos that received the most views received nearly all (∼ 97 %) of their views from the For You page, TikTok's algorithmic recommendation feed. We found that short videos (< 30 s) had a high average view duration, but longer videos (> 60 s) had the highest engagement rates. Lecture-style videos that were approximately 60 s in length had more success in both reach and engagement. Our videos that received the highest number of views featured content that was related to a recent newsworthy event (e.g., an earthquake) or that explained location-based geology of a recognizable area. Our results highlight the algorithm-driven nature of TikTok, which results in a low barrier to entry and success for new science communication creators.

Crustal focal mechanisms in the NW sierras de cordoba, and connections with mio-pliocene basement thrusting of the easternmost Sierras Pampeanas, south-Central Andes

The seismicity studied in this paper is located along the back arc region, between 30°35′ and 31°52’ S latitude, in the morphostructural unit known as Eastern Sierras Pampeanas. Seventeen crustal earthquakes could be identified and located, between June 2004 and March 2018, using seismic data recorded by the broadband seismological network of National Institute for Seismic Prevention (INPRES), combined with free seismic data from the Incorporated Research Institutions for Seismology (IRIS). Focal mechanisms were calculated from localized seismicity using the P-wave first motions and interpreted as a strain style on the western portion of Sierras de Córdoba. Overall, the seismicity in this region during the study period was constrained to the upper ∼25 km of the crust and is mostly concentrated along minor structures and not along the major range-bounding faults. Although there is evidence of quaternary activity along the larger structures, the relationship between these displacements and modern deformations is not well developed due to the lack of local seismic stations in the area and the long recurrence interval between earthquakes of significant magnitudes. However, very recent morphometric studies in the Sierras Pampeanas have analyzed the main topography controls and suggested relatively higher uplift rates in the central sectors of the Sierra de Pocho, and a balance between tectonic uplift and erosion rates. Nevertheless, three seismic events showed greater depths around 36 km according to previously proposed geological and geophysical models of crustal thickness and mohorovicic depth. Although focal mechanism solutions show varied results, distributed throughout all the region, it is possible to determine an inverse deformation with an oblique component assigned to regional faults and an area where a normal deformation with an oblique component predominates, near to the Ojo de Agua Lineament. Accordingly with seismological observations, we proposed a model in which the seismogenic structures seem to have detached from deep horizontal intra-crustal interfaces that affects the faults and brittle structures, which document that the Eastern Sierras Pampeanas are actively deforming in response to compression from the convergent margin.

MTH5: An archive and exchangeable data format for magnetotelluric time series data

Magnetotellurics (MT) is a passive electromagnetic geophysical method that measures variations in subsurface electrical resistivity. MT data are collected in the time domain and processed in the frequency domain to produce estimates of a transfer function representing the Earth’s electrical structure. Unfortunately, the MT community lacks metadata and data standards for time series data. As the community grows and findability, accessibility, interoperability, and reuse of digital assets (FAIR) data principles are enforced by government and funding agencies, a standard is needed for time series data. Presented here is a hierarchical data format (MTH5) that is logically formatted to how MT data are collected. Open-source Python packages are also described to read, write, and manipulate MTH5 files. These include a package to deal with metadata (mt_metadata) based on standards developed by the Working Group for Magnetotelluric Data Handling and Software assembled by the Incorporated Research Institutions for Seismology (IRIS), and mth5: a package to interact with MTH5 files that uses mt_metadata. Example code and workflows are presented.

Mapping Earthquakes in Malawi Using Incorporated Research Institutions for Seismology (IRIS) Catalogue for 1972-2021

Mapping Earthquakes in Malawi Using Incorporated Research Institutions for Seismology (IRIS) Catalogue for 1972-2021

Mapping Earthquakes in Malawi Using Incorporated Research Institutions for Seismology (IRIS) Catalogue for 1972–2021

Mapping Earthquakes in Malawi Using Incorporated Research Institutions for Seismology (IRIS) Catalogue for 1972–2021

3D Seismic Waves Velocity Structure of West Sumatera Seismic Waves Using Earthquake Data from January 2010-December 2017

This study analyses the P wave velocity (Vp) and Vp/Vs based on 3D seismic tomography in West Sumatra. Seismic tomography is a method of reconstructing the image of the subsurface structure of the earth using travel time data. This research uses secondary data obtained from the Incorporated Research Institutions for Seismology (IRIS) from January 2010 to December 2017. The data obtained were 472 earthquake events and 21 seismic stations that recorded the earthquake events. This research consists of are the hypocenter relocation, which will simultaneously renew the 1D velocity model using VELEST software, and tomographic inversion using SIMULPS12 software. The minimum anomaly of Vp/Vs value is around 1.39, while the maximum anomaly Vp/Vs value is around 2.05. The Vp distribution results have low and high Vp/Vs values around Sumatra Fault Zone and Mentawai Fault Zone. Anomaly results from the tomogram of these areas have an association with saturated pressure sedimentary areas and the presence of fractures which will further contribute to earthquake events.

Phased Array Analysis Incorporating the Continuous Wavelet Transform

ABSTRACT Nonlinear block thresholding of the continuous wavelet transform (CWT) of 2D phased array signals offers high time-resolution solutions for analyzing seismograms of local and regional seismic events. An initial denoising step on an array ensemble reveals the regions of the scale-time plane that contain high signal-to-noise arrivals. Individual seismic phase arrivals in ensemble, denoised seismograms can be partitioned using scale-time gating in which CWT wave packets of an individual seismic phase on the scale-time plane for a reference array element are time-correlated with all other elements to find an optimum time shift for the phase across all elements. The seismic phase is then clipped out of the CWT of each array element using this optimal time shift for further analysis. The seismogram can be separated into component seismic waves for a detailed view of wave characteristics such as slowness and arrival azimuth using conventional frequency–wavenumber methods. However, the process can be taken further using the CWT of each phase to construct high time-resolution signal beams over the CWT scale. Local explosion data from the 2016 Incorporated Research Institutions for Seismology (IRIS) Wavefields Community Experiment in northern Oklahoma are used to demonstrate these techniques in separating surface-wave modes and body waves and to examine the scattering of regional phases. High-resolution CWT processing in the 1–3 Hz band for northern Oklahoma reveals horizontal Rayleigh-wave refraction and multipathing. Rayleigh-wave phase-velocity dispersion measurements are used to construct a 1D velocity model under the IRIS experiment. Scale-time gating helps expose near-source surface reflections from a local M 3.6 earthquake that are used to verify the 4 km source depth obtained from a published regional moment tensor solution.

RÉSIF-SI: A Distributed Information System for French Seismological Data

AbstractThe Résif project, which started in 2008, aims at gathering under a common research infrastructure the French seismological, Global Navigation Satellite Systems and gravimeter permanent networks, as well as the mobile instrument pools. A central part of Résif is its seismological information system, Système d'Information de Résif (Résif-SI) (started in 2012), which is in charge of collecting, validating, archiving, and distributing seismological data and metadata from seven national centers. Résif-SI follows a distributed architecture, in which the six data collection and validation centers (A-nodes) send validated data and metadata to a national data center (Résif Data Center [Résif-DC]), which is the central point for data archiving and distribution. Résif-SI is based on international standard formats and protocols, and is fully integrated into European and international data exchange systems (European Integrated Data Archive, European Plate Observing System [EPOS], Incorporated Research Institutions for Seismology, International Federation of Digital Seismograph Networks). In this article, we present the organization of Résif-SI, the technical details of its implementation, and the catalog of services provided to the end users. The article is aimed both at seismologists, who want to discover and use Résif data, and at data center operators, who might be interested in the technical choices made in the implementation of Résif-SI. We believe that Résif-SI can be a model for other countries facing the problem of integrating different organizations into a centralized seismological information system.

The RAMONES Service for Rapid Assessment of Seismic Moment and Radiated Energy in Central Italy: Concepts, Capabilities, and Future Perspectives

Abstract We present Rapid Assessment of MOmeNt and Energy Service (RAMONES), a service for disseminating through a web interface, the estimates of seismic moment (M0) and radiated energy (ER) for earthquakes occurring in central Italy with local magnitudes above 1.7. The service is based on a fully-automatic procedure developed for downloading and processing open seismological data from the European Integrated Data Archive, Italian Civil Protection repository, and Incorporated Research Institutions for Seismology (IRIS). In its actual configuration, RAMONES uses the seismic catalog generated through the event webservice of the Italian Institute of Geophysics and Volcanology (compliant with International Federation of Digital Seismograph Networks standards) to guide the data download. The concept of RAMONES is to estimate M0 and ER from features extracted directly from recordings, namely the S-wave peak displacement (PDS) and the integral of the squared velocity (IV2S) evaluated over the S-wave window at local distances. A data set composed of 6515 earthquakes recorded in central Italy between 2008 and 2018 was used to calibrate the attenuation models relating M0 to PDS and ER to IV2S, including station corrections. The calibration values for M0 and ER were extracted from the source spectra obtained by applying a decomposition approach to the Fourier amplitude spectra known as the generalized inversion technique. To test the capabilities of RAMONES, we validate the attenuation models by performing residual analysis over about 60 earthquakes occurring in 2019 that were used for the spectral decomposition analysis but not considered in the calibration phase. Since January 2020, a testing operational phase has been running, and RAMONES has analyzed about 800 earthquakes by September 2020. The distribution of the source parameters and their relevant scaling relationships are automatically computed and disseminated in the form of maps, parametric tables, figures, and reports available through the RAMONES web interface.

Calibrating the 2016 IRIS Wavefields Experiment Nodal Sensors for Amplitude Statics and Orientation Errors

ABSTRACTWe used teleseismic P and S waves recorded in the course of the 2016 Incorporated Research Institutions for Seismology (IRIS) community-planned experiment in northern Oklahoma, to estimate amplitude correction factors (ACFs) and orientation correction factors (OCFs) for the gradiometer’s three-component Fairfield nodal sensors and two other gradiometer-styled subarray nodal sensors. These subarrays were embedded in the 13 km aperture nodal array that was also fielded during the 2016 IRIS experiment. The array calibration method we used in this study is based on the premise that a common wavefield should be recorded over a small-aperture array using teleseismic observation. In situ estimates of ACF for the gradiometer vary by 2.3% (standard deviation) for the vertical components and, typically, variability is less than 4.3% for the horizontal components; associated OCFs generally dispersed by 3°. For the two subarrays, the vertical-component ACF usually vary up to 2.4%; their horizontal-component ACFs largely spread up to 3.6%. OCFs for the subarrays generally disperse by 6.5°. ACF and OCF estimates for the gradiometer are seen to be stable across frequency bands having high signal coherence and/or signal-to-noise ratio. Gradiometry analyses of calibrated and uncalibrated gradiometer records from a local event revealed notable improvements in accuracy of attributes obtained from analyzing the calibrated horizontal-component waveforms in the light of catalog epicenter-derived azimuth. The improved waveform relative amplitudes after calibration, coupled with the enhanced wave attribute accuracy, suggests that instrument calibration for amplitude statics and orientation errors should be encouraged prior to doing gradiometry analysis in future studies.

Horizontal-to-Vertical Spectral Ratio (HVSR) IRIS Station Toolbox

AbstractThe horizontal-to-vertical spectral ratio (HVSR) for seismic ambient noise is a popular method that can be used to estimate the predominant frequency at a given site. In this article, we introduce the Incorporated Research Institutions for Seismology (IRIS) Data Management Center’s (DMC’s) openly available HVSR station toolbox. These tools offer a variety of ways to compute the spectral ratio by providing different averaging routines. The options range from the simple average of spectral ratios to the ratio of spectral averages. Computations take advantage of the available power spectral density estimates of ambient noise for the seismic stations, and they can be used to estimate the predominant frequency of the many three-component seismic stations available from the IRIS DMC. Furthermore, to facilitate the identification of the peaks in HVSR profiles for the assessment of the predominant frequency of station sites, the toolbox can also process the results of HVSR analysis to detect and rank HVSR peaks. To highlight the toolbox capabilities, three different examples of possible use of this toolbox for routine site-effect analysis are discussed: (1) site effects related to thawing in Arctic regions, (2) ground-motion amplification in urban area, and (3) estimation of station VS30.

The Alaska Transportable Array: As Built

Abstract Alaska is the last frontier and final destination for the National Science Foundation-supported EarthScope USArray Transportable Array (TA) project. The goal of this project is to record earthquakes and image the structure of the North American continent. The Alaska TA consists of 283 broadband seismic stations evenly spaced about 85 km apart to cover the state of Alaska and into western Canada. The sensor emplacement technique and station design were developed specifically for superior performance—both in terms of seismic noise levels and station durability. This technique and design were used for the 194 new stations installed as well as the 32 existing broadband stations that were upgraded. Trial stations were installed in 2011–2013 as part of a process to test and refine the installation design. The main deployment began in 2014 using the final station design and was completed in 2017. From 2018 through 2020, Incorporated Research Institutions for Seismology (IRIS) operated the Alaska TA by performing servicing, station improvements, and data quality monitoring. High data return was maintained throughout, though some stations had lower real-time data delivery in winter. 110 TA stations are expected to transition to other operators in 2019 and 2020, and the data from these are openly available under new network codes. The last 84 stations are expected to be removed during the 2021 field season to close out the TA project. The Alaska TA was installed safely despite a challenging environment and has been operated to maximize the continuity and quality of data collected across a vast geographic region, enabling exciting scientific research for years to come.

A Case Study of Highly-Engaged Educators' Integration of Real-Time Seismic Data in Secondary Classrooms

The Incorporated Research Institutions for Seismology (IRIS) Seismographs in Schools (SIS) program has supported teachers in the use of educational seismometers and real-time seismic data in the classroom for the past 20 years. To better understand how the seismographs and seismic data are being used in the classroom, we sent a survey to 770 past or current program participants. The survey asked about their seismometer, seismic data use, software use, the impact of seismic data on their classroom, and what additional seismology-related resources or instruction they provide to their students. Four highly-engaged teachers were then recruited from this larger pool for a case study. The purpose of this study was to better understand these highly-engaged teachers, their experiences with seismic instrumentation, software and data in the classroom, how and to what degree seismic data has impacted their curriculum and instruction, and their perceptions of the impact of the SIS program on their students’ understanding of Earth Science concepts. The case study results show that each of the highly-engaged teachers values data driven instruction, instrument science, and the integration of seismic data into the classroom more than just during their earthquake units. They have made it part of everyday class activities by having students be aware of data coming in, noting earthquakes in the news, and helping students learn more about analyzing data for advanced investigations. While there were differences in their implementations, in all cases a critical feature of their engagement with students was use of a variety of seismology-related resources which connected the seismic data to the rest of the curriculum. Thus, the use of seismic data was just one component of their seismology-related teaching. This study also highlights the value of a local sensor, as all four highly-engaged teachers stressed that students as stewards of the seismometer linked them to the science in an engaging and dynamic way. Thus, while the highly-engaged teachers had a primary responsibility to promote learning, their focus on student engagement is also helping to create young citizen scientists.

Precision Seismic Monitoring and Analysis at Axial Seamount Using a Real‐Time Double‐Difference System

AbstractSeven three‐component ocean bottom seismometers (OBS) of the Ocean Observatories Initiative (OOI) Cabled Array on top of Axial Seamount are continuously streaming data in real time to the Incorporated Research Institutions for Seismology (IRIS). The OBS array records earthquakes from the submarine volcano which last erupted on 24 April 2015, about 4 months after the array came online. The OBS data have proven crucial in providing insight into the volcano structure and dynamics (Wilcock et al., 2016, https://doi.org/10.1126/science.aah5563). We implemented a real‐time double‐difference (RT‐DD) monitoring system that automatically computes high‐precision (tens of meters) locations of new earthquakes. The system's underlying double‐difference base catalog includes nearly 100,000 earthquakes and was computed using kurtosis phase onset picks, cross‐correlation phase delay times, and 3‐D P and S velocity models to predict the data. The relocations reveal the fine‐scale structures of long‐lived, narrow (<200 m wide), outward dipping, convex faults on the east and west walls of the caldera that appear to form a figure 8‐shaped ring fault system. These faults accommodate stresses caused by the inflation of magma prior to and deflation during eruptions. The east fault is segmented and pulled apart in east‐west direction due to its interaction with the Juan de Fuca Ridge, which at this location forms an overlapping spreading center. The RT‐DD system enables the monitoring and rapid analysis of variations in fine‐scale seismic and fault properties and has the potential to improve prediction of timing and location of the next Axial eruption expected to occur in the 2022–2023 time frame.

An array-based receiver function deconvolution method: methodology and application

SUMMARYReceiver functions (RFs) estimated on dense arrays have been widely used for the study of Earth structures across multiple scales. However, due to the ill-posedness of deconvolution, RF estimation faces challenges such as non-uniqueness and data overfitting. In this paper, we present an array-based RF deconvolution method in the context of emerging dense arrays. We propose to exploit the wavefield coherency along a dense array by joint inversions of waveforms from multiple events and stations for RFs with a minimum number of phases required by data. The new method can effectively reduce the instability of deconvolution and help retrieve RFs with higher fidelity. We test the algorithm on synthetic waveforms and show that it produces RFs with higher interpretability than those by the conventional RF estimation practice. Then we apply the method to real data from the 2016 Incorporated Research Institutions for Seismology (IRIS) community wavefield experiment in Oklahoma and are able to generate high-resolution RF profiles with only three teleseismic earthquakes recorded by the temporary deployment. This new method should help enhance RF images derived from short-term high-density seismic profiles.

Using Seismic Source Parameters to Model Frequency-Dependent Surface-Wave Radiation Patterns

AbstractThe excitation of surface waves depends on the frequency-dependent eigenfunctions of the Earth, which are determined numerically. As a consequence, radiation patterns of Rayleigh and Love waves cannot be calculated analytically and vary with source depth and with frequency. Owing to the importance of surface-wave amplitudes for inversions of source processes as well as studies of the elastic and anelastic structure of the Earth, assessing surface-wave radiation patterns for different source mechanisms is desirable. A data product developed in collaboration with the Incorporated Research Institutions for Seismology (IRIS) Consortium provides visualizations of the radiation patterns for Rayleigh and Love waves for all possible source mechanisms. Radiation patterns for known earthquakes are based on the moment tensors reported by the Global Centroid Moment Tensor project. These source mechanisms can be modified or moment tensor components can be chosen by the user to assess their effect on Rayleigh- and Love-wave radiation patterns.