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It is suggested that in addition to seismicity deep fluid injection may cause surface uplift and subsidence in oil and gas-producing regions. This study uses the Raton Basin as an example to investigate the hydromechanical processes of surface uplift and subsidence during wastewater injection. The Raton Basin, in southern central Colorado and northern central New Mexico, has experienced wastewater injection related to coalbed methane and gas production starting in 1994. In this study, we estimate the extent and magnitude of total vertical deformation in the Raton Basin from 1994 to 2020 and incremental deformation between the years 2017 to 2020. Results indicate a modeled uplift as much as 15 cm occurring between 1994 and 2020. Between 2017 and 2020, up to 3 cm of uplift occurred, largely near the northwestern injection wells. Most modeled uplift between 1994 and 2020 occurred near the southern wells, where the greatest cumulative volume of wastewater was injected. However, modeled subsidence occurred around the southern and eastern wells between 2017 and 2020, after the rate of injection decreased. Modeling indicates that while the magnitude of modeled uplift corresponds to cumulative injection volume and maximum rate in the long-term, short-term incremental deformation (uplift or subsidence) is controlled by changes in the rate of injection. The number of yearly earthquake events follows periods of rapid modeled uplifting throughout the Basin, suggesting that measurable surface deformation may be caused by the same injection-induced pore pressure perturbations that initiate seismicity., (© 2024 The Authors. Groundwater published by Wiley Periodicals LLC on behalf of National Ground Water Association.)

The Regional Earthquake Likelihood Models (RELM) test of earthquake forecasts in California was the first competitive evaluation of forecasts of future earthquake occurrence. Participants submitted expected probabilities of occurrence of M ≥ 4.95 earthquakes in 0.1° × 0.1° cells for the period 1 January 1, 2006, to December 31, 2010. Probabilities were submitted for 7,682 cells in California and adjacent regions. During this period, 31 M ≥ 4.95 earthquakes occurred in the test region. These earthquakes occurred in 22 test cells. This seismic activity was dominated by earthquakes associated with the M = 7.2, April 4, 2010, El Mayor-Cucapah earthquake in northern Mexico. This earthquake occurred in the test region, and 16 of the other 30 earthquakes in the test region could be associated with it. Nine complete forecasts were submitted by six participants. In this paper, we present the forecasts in a way that allows the reader to evaluate which forecast is the most "successful" in terms of the locations of future earthquakes. We conclude that the RELM test was a success and suggest ways in which the results can be used to improve future forecasts.

In weather forecasting, current and past observational data are routinely assimilated into numerical simulations to produce ensemble forecasts of future events in a process termed “model steering”. Here we describe a similar approach that is motivated by analyses of previous forecasts of the Working Group on California Earthquake Probabilities (WGCEP). Our approach is adapted to the problem of earthquake forecasting using topologically realistic numerical simulations for the strike-slip fault system in California. By systematically comparing simulation data to observed paleoseismic data, a series of spatial probability density functions (PDFs) can be computed that describe the probable locations of future large earthquakes. We develop this approach and show examples of PDFs associated with magnitude M > 6.5 and M > 7.0 earthquakes in California.

The Himalayan belt, formed due to Cenozoic convergence between the Eurasia and Indian craton, acts as a storehouse of large amounts of strain that results in large earthquakes that occur from the western to the eastern Himalayas. Glaciers also occur over a major portion of the high-altitude Himalayan region. In this study, we attempt to understand the impact of earthquakes on and around Himalayan glaciers in terms of vertical deformation and coherence change. Eight earthquake events of various magnitudes and hypocenter depths occurring in the vicinity of Himalayan glacial bodies have been analyzed using C-band Sentinel1-A/B synthetic aperture radar (SAR). Differential interferometric SAR (DInSAR) method is applied to the pre-and co-seismic single look complex (SLC) SAR imagery to capture glacial surface deformation potentially related to earthquake occurrence. The influence radius of each earthquake (Mw>4.5) is defined using shake maps. For the lower magnitude earthquakes (Mw<4.5), influence radii are computed using the linear relationship between influence radii and magnitudes of past earthquakes. The mean glacial displacement varies from -38.9 mm to -5.4 mm for the 2020 Tibet earthquake (Mw 5.7) and the 2021 Nepal earthquake (Mw 4.1). However, small glacial and ground patches processed separately for vertical displacements reveal that the glacial mass shows much greater seismic displacement than the ground surface. This indicates potential site-specific seismicity amplification properties of glacial bodies that need additional studies. Reduction in co-seismic coherence around the glaciers is observed in some cases, indicative of possible changes in the glacial moraine deposits and/or vegetation cover. The effect of two different seismic events (the 2020 and 2021 Nepal earthquakes) with different hypocenter depths but the same magnitude at almost equal distances from the glaciers is assessed; a shallow earthquake is observed to result in a larger impact on glacial bodies in terms of vertical displacement. Earthquakes may exacerbate or induce glacial hazards such as glacial surging, ice avalanches, landslides and failure of moraine-/ice-dammed glacial lakes. This research can assist in identifying areas at risk and provide valuable insights for planning and implementing measures for disaster risk reduction in the near future. [ABSTRACT FROM AUTHOR]

The volcanic eruption at La Palma started on September 19, 2021. The eruption was preceded by a seismic swarm that began on September 11, although anomalous seismicity has been observed on the island since 2017. During the co-eruptive phase of the seismic activity, hypocenters depth was generally less than 15 km, save for the period between November 10 and November 27, when hypocenters ranged in the depth from 15 to 40 km. The eruption ended on December 13, 2021. We compute tidal stress for each earthquake at the hypocenter depth and find statistically significant correlations between the occurrence times of the earthquakes and the confining tidal stress values and stress rates. The correlation is depth-dependent, and ocean-loading tides have a stronger effect than body tides. We find that tidal stress variations contribute to the eruption onset and that certain explosive events, typical in Strombolian type volcanoes, seem to occur preferentially when the tidal stress rate is high. Our analysis supports the hypothesis that tides may modulate earthquake activity in volcanic areas, specifically during magma migration at shallow depths. A conceptual model is proposed, which could have a general application in the Canary Islands archipelago and other volcanic islands. [ABSTRACT FROM AUTHOR]

The Raton Basin of Southern Colorado and Northern New Mexico experienced a significant increase in seismicity over the last several decades, including two M5+ earthquakes. The increase in seismicity started soon after an increase in wastewater disposal associated with coal‐bed methane production. Twenty‐nine wastewater injection wells have operated in the Basin, with several high‐rate injectors located within a kilometer of the most seismically active regions. We developed a pore pressure model to investigate the relationship between pore pressure diffusion and onset of induced seismicity, with an emphasis on the Trinidad fault zones. Our model indicates that sufficient pore pressure increase had accumulated on the northern extent of the Trinidad fault zone to induce seismicity at the time of early‐stage seismic activity. The hydrogeologic architecture of the Basin played a key role in controlling pore pressure perturbation. The basal sedimentary interval with moderately low diffusivity restricted vertical pore pressure diffusion, creating a substantial lag time between wells becoming active and the expression of perturbation in the fault zones. The spatiotemporal relationship between early‐stage seismicity and wastewater injection in conjunction with modeled pore pressures suggests that the early‐stage seismicity in the Raton Basin was likely triggered by pore pressure diffusion. Plain Language Summary: In the Raton Basin, coal‐bed methane production sparked the need for deep wastewater disposal starting in 1994. Prior to wastewater injection few earthquakes were recorded within its boundaries but a large increase in earthquakes has been recorded over the last several decades. Pore pressure increase, caused by the deep wastewater injection, is thought to be the reason for the increase in local earthquakes. We developed a model to estimate pore pressure increases on several fault zones that have recently exhibited increased earthquake frequency. We found that wastewater injection produced increases in pore pressure on the fault zones large enough to cause earthquakes. This suggests that increased seismicity is, at least in part, the result of pore pressure change caused by deep wastewater injection. Key Points: Pore pressure change between 0.007 and 0.03 MPa initiates the onset of induced seismicity on the Trinidad fault zoneThe basal sedimentary interval restricted pore pressure diffusion, limiting the impact of high‐rate injection wells in the short termThe depth varying permeability of crystalline basement effects the manner and magnitude of pore pressure diffusion into basement faults [ABSTRACT FROM AUTHOR]

The aim of the present study is to analyze the occurrences of future earthquakes using forecasting techniques from past seismicity in northeast India (latitude 20°N–31°N and longitude 87°E–97°E). The present study applies two types of retrospective binary forecasting. The first one is the pattern informatics (PI) method and the other is the Relative Intensity (RI) method. These techniques quantify the spatio-temporal seismicity rate changes in the historic seismicity of the study region. For this purpose, a uniform and complete earthquake catalogue in moment magnitude (Mw > 3) is prepared. The resulting binary forecasts are evaluated with the relative operating characteristics (ROC) diagram. The ROC diagram quantifies the results in terms of a hit rate (fraction of events that are successfully forecasted) versus a false alarm rate (no event occurs in a hotspot box). Evaluation of forecasting results using ROC diagram is more protective than maximum likelihood tests. The result gives a regional seismogenic map where earthquakes are likely to occur during a specified period in the future. The recent India–Nepal border earthquake of 18 September 2011 occurred in one of the forecasted regions. These techniques have been applied for the first time to the Indian subcontinent. [ABSTRACT FROM AUTHOR]

Seismic hazard maps are a significant input into emergency hazard management that play an important role in saving human lives and reducing the economic effects after earthquakes. Despite the fact that a number of software tools have been developed (McGuire, 1976, 1978; Bender & Perkins, 1982, 1987; Robinson et al., 2005, 2006; Field et al., 2003), map resolution is generally low, potentially leading to uncertainty in calculations of ground motion level and underestimation of the seismic hazard in a region. In order to generate higher resolution maps, the biggest challenge is to handle the significantly increased data processing workload. In this study, a method for improving seismic hazard map resolution is presented that employs a pipelining implementation of the existing EqHaz program suite (Assatourians & Atkinson, 2013) based on IBM InfoSphere Streams–an advanced stream computing platform. Its architecture is specifically configured for continuous analysis of massive volumes of data at high speeds and low latency. Specifically, it treats processing workload as data streams. Processing procedures are implemented as operators that are connected to form processing pipelines. To handle large processing workload, these pipelines are flexible and scalable to be deployed and run in parallel on large-scale HPC clusters to meet application performance requirements. As a result, mean hazard calculations are possible for maps with resolution up to 2,500,000 points with near-real-time processing time of approximately 5-6 minutes. [ABSTRACT FROM AUTHOR]

Abstract: Earthquake fault systems interact over a broad spectrum of spatial and temporal scales and, in recent years, studies of the regional seismicity in a variety of regions have produced a number of new techniques for seismicity-based earthquake forecasting. While a wide variety of physical assumptions and statistical approaches are incorporated into the various methodologies, they all endeavor to accurately replicate the statistics and properties of both the historic and instrumental seismic records. As a result, the last ten years have seen significant progress in the field of intermediate- and short-term seismicity-based earthquake forecasting. These include general agreement on the need for prospective testing and successful attempts to standardize both evaluation methods and the appropriate null hypotheses. Here we differentiate the predominant approaches into models based upon techniques for identifying particular physical processes and those that filter, or smooth, the seismicity. Comparison of the methods suggests that while smoothed seismicity models provide improved forecast capability over longer time periods, higher probability gain over shorter time periods is achieved with methods that integrate statistical techniques with our knowledge of the physical process, such as the epidemic-type aftershock sequence (ETAS) model or those related to changes in the b-value, for example. In general, while both classes of seismicity-based forecasts are limited by the relatively short time period available for the instrumental catalog, significant advances have been made in our understanding of both the limitations and potential of seismicity-based earthquake forecasting. There is general agreement that both short-term forecasting, on the order of days to weeks, and longer-term forecasting over five-to-ten year periods, is within reach. This recent progress serves to illuminate both the critical nature of the different temporal scales intrinsic to the earthquake process and the importance of high quality seismic data for the accurate quantification of time-dependent earthquake hazard. [Copyright &y& Elsevier]

The Cushing Hub in Oklahoma, one of the largest oil storage facilities in the world, is federally designated as critical national infrastructure. In 2014, the formerly aseismic city of Cushing experienced a Mw 4.0 and 4.3 induced earthquake sequence due to wastewater injection. Since then, an M4+ earthquake sequence has occurred annually (October 2014, September 2015, November 2016). Thus far, damage to critical infrastructure has been minimal; however, a larger earthquake could pose significant risk to the Cushing Hub. In addition to inducing earthquakes, wastewater injection also threatens the Cushing Hub through gradual surface uplift. To characterize the impact of wastewater injection on critical infrastructure, we use Differential Interferometric Synthetic Aperture Radar (DInSAR), a satellite radar technique, to observe ground surface displacement in Cushing before and during the induced Mw 5.0 event. Here, we process interferograms of Single Look Complex (SLC) radar data from the European Space Agency (ESA) Sentinel-1A satellite. The preearthquake interferograms are used to create a time series of cumulative surface displacement, while the coseismic interferograms are used to invert for earthquake source characteristics. The time series of surface displacement reveals 4–5.5 cm of uplift across Cushing over 17 months. The coseismic interferogram inversion suggests that the 2016 Mw 5.0 earthquake is shallower than estimated from seismic inversions alone. This shallower source depth should be taken into account in future hazard assessments for regional infrastructure. In addition, monitoring of surface deformation near wastewater injection wells can be used to characterize the subsurface dynamics and implement measures to mitigate damage to critical installations. [ABSTRACT FROM AUTHOR]

Sub-lithospheric stresses can be estimated by analysis of gravity field measurements. Depending on the measured gravimetric quantity, different methods can be employed to estimate those sub-lithospheric stresses. Here, we further develop the Runcorn’s theory for estimation of mantle stresses (1967) such that a Moho model and full topographic information are used to recover the function from which the stress can be computed by taking derivatives northwards and eastwards. We develop new integral equations for such a purpose and recover this function by solving those integral equations locally over the Indo-Pak (India-Pakistan) region from (1) a gravimetric Moho model computed from the SRTM (Shuttle Radar Topography Mission) and the Earth gravity model EGM2008, (2) SRTM and the seismic Moho model of CRUST1.0 and (3) data and measurements of the GOCE (Gravity field and steady-state Ocean Circulation Explorer) mission. Finally, we perform a joint inversion of seismic and GOCE data for the same purpose. The numerical results show that the use of a seismic Moho model recovers information about the stress field which is not seen in the results derived from a gravimetric Moho model. A combination of the seismic Moho model, SRTM and GOCE yields a better stress field than that of either the seismic and/or gravimetric data alone. The magnitudes of the sub-lithospheric stress are computed from the shear stress components over the area and good agreement is seen between the recovered combined stress field, the regional tectonic boundaries and the seismicity of the World Stress Map 2008 database. [ABSTRACT FROM AUTHOR]

Many driven threshold systems display a spectrum of avalanche event sizes, often characterized by power-law scaling. An important problem is to compute probabilities of the largest events ("Black Swans"). We develop a data-driven approach to the problem by transforming to the event index frame, and relating this to Shannon information. For earthquakes, we find the 12-month probability for magnitude m > 6 earthquakes in California increases from about 30% after the last event, to 40%-50% prior to the next one. [ABSTRACT FROM AUTHOR]