nasa-gesdisc/es-publications-researchareas huggingface dataset:
Precursors of quasi-decadal dry-spells in the Central America Dry Corridor (2019)

Although the hydric stress in Central America is generally low, there is a region relatively drier and prone to drought known as the Central America Dry Corridor (CADC). The area of interest is located mainly in the Pacific slope of Central America, from Chiapas in southern Mexico, to the Nicoya Peninsula in the Costa Rican North Pacific. Most of the region has experienced significant warming trends (19701999). On the contrary precipitation and the Palmer Drought Severity Index (PDSI) have mainly displayed non-significant trends. Analysis using the Standardized Precipitation Index and PDSI in the CADC, suggests a significant periodicity of severe and sustained droughts of around 10 years. The drought response has been associated with tropical heating that drives an atmospheric response through strengthening of the Hadley cell, which in turn produces higher pressure in the subtropical highs, and intensification of the trade winds (indexed by the Caribbean Low Level Jet). It is important to determine the commonness of severe and sustained droughts in the CADC to improve water resources planning, as this is a region that depends on subsistence agriculture and presents high social and economic vulnerabilities.

Research areas: Droughts
Water as destiny–The long-term impacts of drought in sub-Saharan Africa (2019)

We examine the long-term impacts of drought exposure on women born in 19 countries in sub-Saharan Africa, across four decades. We find that women who were exposed to drought conditions during their early childhood are significantly less wealthy as adults. These effects are confined to women born and raised in rural households, indicating that the impacts of rainfall are felt via changes in agricultural output. In addition to lower levels of wealth, women who experience droughts in infancy also receive fewer years of formal education and, in the case of extreme drought conditions, have reduced adult heights. Our results also suggest that drought exposure in infancy can have long-term, negative impacts on womens empowerment. Finally, we also show that these impacts may be transmitted to the womens offspring, with children of affected women more likely to be born at a low birth weight (weighing <2.5 kg). To our knowledge, this represents the largest study to date both geographically and over time showing a strong relationship between early life rainfall conditions and adult outcomes, and the first to show that the impacts could span generations.

Research areas: Droughts, Public Health
Response of vegetation to the 2003 European drought was mitigated by height (2014)

Abstract. The effects on climate of land-cover change, predominantly from the conversion of forests to crops or grassland, are reasonably well understood for low and high latitudes but are largely unknown for temperate latitudes. The main reason for this gap in our knowledge is that there are compensating effects on the energy and water balance that are related to changes in land-surface albedo, soil evaporation and plant transpiration. We analyse how vegetation height affected the response of vegetation during the 2003 European drought using precipitation data, temperature data, normalized difference vegetation index data and a new vegetation height data set obtained from the Geoscience Laser Altimeter System (GLAS) on the Ice, Cloud and land Elevation Satellite (ICESat). At the height of the 2003 drought we find for tall vegetation a significantly smaller decrease in vegetation index and a smaller diurnal temperature (DTR) range, indicating less water stress and drought impacts on tall vegetation. Over Germany for example, 98% of significant correlations showed a smaller anomaly in vegetation index anomaly with greater height, and 95% of significant correlations showed a smaller DTR with greater vegetation height. Over France the equivalent percentages were 94 and 88%, respectively. Vegetation height is likely associated with greater rooting depth, canopy heat capacity or both. Our results suggest that land-surface models can be improved by better estimates of vegetation height and associated with this a more realistic response to drought.

Research areas: Droughts, Land Surface/Agriculture Indicators
Enhancing the standardized drought vulnerability index by integrating spatiotemporal information from satellite and in situ data (2018)

Drought is a complex natural hazard with its adverse multifaceted impacts cascading in every physical and human system. The vulnerability magnitude of various areas to drought mostly depends on their exposure to water deficiency, the existing water management policy framework and its implementation. The Standardized Drought Vulnerability Index (SDVI) is an integrated attempt towards characterizing drought vulnerability based on a comparative classification system, incorporating precipitation patterns, the supply and demand trends, and the socioeconomic background as the most crucial contributors to drought vulnerability. This work attempts to evolve the SDVI by presenting a more rigorous method of index parameters estimation and argues that the combination of in-situ and satellite data improve the index results in an effort to further minimize the paucity of drought related information. At the same time, it helps to surpass previous limitations in temporal and spatial propagation of the vulnerability concept. The new framework is applied in the South Platte Basin, within Colorado, on the 2012 summer drought (July-September). The proposed index modification may convey drought information in a more holistic manner to decision makers. SDVI could aid in advancing the understanding of each component contribution through in situ and remote sensing data integration and in avoiding existing practices of broken linkages and fragmentation of the reported impacts. Thus, it is believed that the SDVI could serve as an additional tool to guide decisions and target mitigation and adaptation actions, allowing for a more integrated management approach.

Research areas: Droughts
Cascading DroughtHeat Dynamics During the 2021 Southwest United States Heatwave (2022)

In June of 2021 the Southwest United States experienced a record-breaking heatwave. This heatwave came at a time when the region was in severe drought. As drought alters the surface energy budget in ways that affect lower atmosphere temperature and circulations, it is possible that the combined drought-heat event was a cascading climate hazard, in which preexisting drought exacerbated the heatwave. We apply satellite observation and numerical experiments with the Weather Research and Forecasting (WRF) model to test for land-atmosphere feedbacks during the heatwave consistent with drought influence. We find a modest positive drought-heat effect, as WRF simulations that include the drought have marginally higher air temperatures than those that exclude the initial drought conditions, with more substantial effects in wetter, forested areas. Evidence of drought-heat-drought-coupled feedbacks was similarly modest in our simulations, as accounting for drought preconditioning led to a small reduction in simulated precipitation in the region.

Research areas: Droughts, Heat
Earthquakes on the surface: earthquake location and area based on more than 14 500 ShakeMaps (2018)

Abstract. Earthquake impact is an inherently interdisciplinary topic that receives attention from many disciplines. The natural hazard of strong ground motion is the reason why earthquakes are of interest to more than just seismologists. However, earthquake shaking data often receive too little attention by the general public and impact research in the social sciences. The vocabulary used to discuss earthquakes has mostly evolved within and for the discipline of seismology. Discussions on earthquakes outside of seismology thus often use suboptimal concepts that are not of primary concern. This study provides new theoretic concepts as well as novel quantitative data analysis based on shaking data. A dataset of relevant global earthquake ground shaking from 1960 to 2016 based on USGS ShakeMap data has been constructed and applied to the determination of past ground shaking worldwide. Two new definitions of earthquake location (the shaking center and the shaking centroid) based on ground motion parameters are introduced and compared to the epicenter. These definitions are intended to facilitate a translation of the concept of earthquake location from a seismology context to a geographic context. Furthermore, the first global quantitative analysis on the size of the area that is on average exposed to strong ground motion  measured by peak ground acceleration (PGA)  is provided.

Research areas: Earthquakes
Using space observation techniques to study temporal and spatial characteristics of seismogenic process, occurrence and deformation of the Qinghai Madoi MW7.4 … (2022)

In order to reveal the characteristics of pre-seismic deformation and co-seismic rupture of the 2021 Qinghai Madoi MW7.4 earthquake, we systematically collect the GNSS data from Qinghai CORS and Crustal Movement Observation Network of China and the SAR data from Sentinel-1 and ALOS-2 satellites, and obtain the dynamic deformation field of the Madoi earthquake by the integrated processing of multi-source data. The pre-seismic GNSS deformation field shows that the Madoi focal area is located at the edge of the high-value region of shear deformation in the north of the earthquake, and sinistral shear strain was accumulated there before the earthquake. The 3-D co-seismic deformation field shows that the KunlunshanPass-Jiangcuo fault has a significant sinistral rupture, and the co-seismic deformation mainly occurs within 100 km from the fault with a maximum horizontal component of 2.4 m. The vertical co-seismic deformation mainly occurs in the vicinity of the fault, and shows alternately positive and negative variation from one side of the fault to the other, which reveals the spatial diversity of dip angles of the ruptured fault. The result of the joint inversion of GNSS and InSAR shows that the rupture of the Madoi earthquake reaches the surface, which is mainly distributed above 15 km depth, with the maximum slip value at about 4 m, and the moment magnitude is about 7.4. The rupture along the fault strike shows an obvious segmental characteristic, and five regions with significant slip values are distributed discontinuously.

Research areas: Earthquakes
Constraining Properties of Sedimentary Strata Using Receiver Functions: An Example from the Atlantic Coastal Plain of the Southeastern United States (2020)

Thickness and seismic velocities of sedimentary sequences strongly affect their response during earthquakes, which can prolong and amplify ground motions. We characterize shallow structure of Atlantic Coastal Plain (ACP) sediments using a passiveseismic approach based on highfrequency PtoS receiver functions. We map the sitespecific fundamental frequency for 64 USArray Transportable Array stations and confirm that the method yields results similar to those from traditional spectral ratio techniques, with fundamental frequencies between 0.1 and 1 Hz. In addition, using sediment Swave reverberations and PtoS phase arrival times measured directly from the receiver functions, we invert for average S and Pwave velocity profiles of the ACP sedimentary strata. We find that VS increases with depth following a powerlaw relationship (VSz) whereas the increase of VP with depth is more difficult to constrain using converted wave methods; therefore, we choose to use the Brocher (2005) relationship to obtain VP through a VP/VS relationship. Finally, we use the variation of measured Sreverberation amplitudes with depth to validate these velocity profiles. These results have implications for seismic shaking across the ACP, which covers large portions of the eastern United States.

Research areas: Earthquakes
Real‐Time Performance of the PLUM Earthquake Early Warning Method during the 2019 6.4 and 7.1 Ridgecrest, California, Earthquakes (2020)

We evaluate the timeliness and accuracy of groundmotionbased earthquake early warning (EEW) during the July 2019 M 6.4 and 7.1 Ridgecrest earthquakes. In 2018, we began retrospective and internal realtime testing of the propagation of local undamped motion (PLUM) method for earthquake warning in California, Oregon, and Washington, with the potential that PLUM might one day be included in the ShakeAlert EEW system. A realtime version of PLUM was running on one of the ShakeAlert EEW systems development servers at the time of the 2019 Ridgecrest sequence, allowing us to evaluate the timeliness and accuracy of PLUMs warnings for the M 6.4 and 7.1 mainshocks in real time with the actual data availability and latencies of the operational ShakeAlert EEW system. The latter is especially important because highdata latencies during the M 7.1 earthquake degraded ShakeAlerts performance. PLUM proved to be largely immune to these latencies. In this article, we present a retrospective analysis of PLUM performance and explore three potential regional alerting strategies ranging from spatially large regions (counties), to moderatesize regions (National Weather Service public forecast zones), to highspatial specificity (50 km regular geographic grid). PLUM generated initial shaking forecasts for the two mainshocks 5 and 6 s after their respective origin times, and faster than the ShakeAlert systems first alerts. PLUM was also able to accurately forecast shaking across southern California for all three alerting strategies studied. As would be expected, a costbenefit analysis of each approach illustrates tradeoffs between increasing warning time and minimizing the area receiving unneeded alerts. Choosing an optimal alerting strategy requires knowledge of users false alarm tolerance and minimum required warning time for taking protective action, as well as the time required to distribute alerts to users.

Research areas: Earthquakes
Consecutive statistical evaluation framework for earthquake forecasting: Evaluating satellite surface temperature anomaly detection methods (2022)

Short-term earthquake prediction remains a challenge. In this study, we investigated earthquake predictability using a consecutive statistical evaluation framework (CSEF). Two widely used anomaly detection methodsZ-score (ZS) and Robust Satellite Techniques (RST)were evaluated using the Atmospheric Infrared Sounder surface temperature data based on global M  6 earthquakes with focal depths of 70 km from 2006 to 2020. Retrospective correlation analyses reveal accuracy and missed detection rates of 80.33% & 19.67% and 80.93% & 19.67% for ZS and RST, respectively. For earthquake forecasting performance in seismically active regions, accuracy rates are within 01% and false alarm rates are up to 5080%. Areas near earthquake-prone regions have the highest accuracy rates. The accuracy rates can be >10% within some regions in Japan and Indonesia. Overall temporal average Matthews correlation coefficients (MCC) range from 0.48 to 0.21; global spatial average MCCs for each day from 2006 to 2020 are between 0.1 and 0.1. After 2012, the ZS method yields higher MCC values than the RST method. Our results confirm the reliability of CESF for assessment of earthquake forecasting capability, and the possibility of forecasting earthquakes at earthquake-prone areas. This approach can be applied to long-term analyses of precursory parameters, anomaly detection methods, and hypotheses, all of which are essential to the ultimate goal of routine and consistent earthquake forecasting.

Research areas: Earthquakes
Exposure forecasting for seismic risk estimation: Application to Costa Rica (2021)

This study proposes a framework to forecast the spatial distribution of population and residential buildings for the assessment of future disaster risk. The approach accounts for the number, location, and characteristics of future assets considering sources of aleatory and epistemic uncertainty in several time-dependent variables. The value of the methodology is demonstrated at the urban scale using an earthquake scenario for the Great Metropolitan Area of Costa Rica. Hundreds of trajectories representing future urban growth were generated using geographically weighted regression and multiple-agent systems. These were converted into exposure models featuring the spatial correlation of urban expansion and the densification of the built environment. The forecasted earthquake losses indicate a mean increase in the absolute human and economic losses by 2030. However, the trajectory of relative risk is reducing, suggesting that the long-term enforcement of seismic regulations and urban planning are effectively lowering seismic risk in the case of Costa Rica.

Research areas: Earthquakes
Insights into seismogenic deformation during the 2018 Hualien, Taiwan, earthquake sequence from InSAR, GPS, and modeling (2019)

We provide new data and insights into a 6 February 2018 Mw 6.4 earthquake that shook the city of Hualien in eastern Taiwan at the leading edge of a modern arccontinent collision. Fatalities and damages were concentrated near the Milun fault and extended south to the northern Longitudinal Valley fault. Although the Hualien area has one of the highest rates of seismicity in Taiwan, the geologic structures responsible for active deformation were not well understood before this event. We analyzed Interferometric Synthetic Aperture Radar (InSAR) and Global Positioning System (GPS) data and produced a 3D displacement model with InSAR and azimuth offset of radar images to document surface deformation induced by this earthquake. The 3D displacement model was inverted to estimate slip on the Milun fault. We find that models assuming a single fault are inconsistent with observations of coseismic deformation and regional strain patterns, providing evidence for linked slip on a littlestudied offshore thrust belt. Based on data presented here and elsewhere, we propose a model for transpressive deformation in a zone of oblique convergence and leftlateral wrench tectonics to explain this and a prior 1951 M 7.3 earthquake.

Research areas: Earthquakes
Visual Analysis of Spatiotemporal Phenomena with 1D Projections (2021)

AbstractIt is crucial to visually extrapolate the characteristics of their evolution to understand critical spatiotemporal events such as earthquakes, fires, or the spreading of a disease. Animations embedded in the spatial context can be helpful for understanding details, but have proven to be less effective for overview and comparison tasks. We present an interactive approach for the exploration of spatiotemporal data, based on a set of neighborhoodpreserving 1D projections which help identify patterns and support the comparison of numerous time steps and multivariate data. An important objective of the proposed approach is the visual description of local neighborhoods in the 1D projection to reveal patterns of similarity and propagation. As this locality cannot generally be guaranteed, we provide a selection of different projection techniques, as well as a hierarchical approach, to support the analysis of different data characteristics. In addition, we offer an interactive exploration technique to reorganize and improve the mapping locally to users' foci of interest. We demonstrate the usefulness of our approach with different realworld application scenarios and discuss the feedback we received from domain and visualization experts.

Research areas: Validation
Possible correlation between annual gravity change and shallow background seismicity rate at subduction zone by surface load (2017)

The Gravity Recovery and Climate Experiment (GRACE) has monitored global gravity changes since 2002. Gravity changes are considered to represent hydrological water mass movements around the surface of the globe, although fault slip of a large earthquake also causes perturbation of gravity. Since surface water movements are expected to affect earthquake occurrences via elastic surface load or pore-fluid pressure increase, correlation between gravity changes and occurrences of small (not large) earthquakes may reflect the effects of surface water movements. In the present study, we focus on earthquakes smaller than magnitude 7.5 and examine the relation between annual gravity changes and earthquake occurrences at worldwide subduction zones. First, we extract amplitudes of annual gravity changes from GRACE data for land. Next, we estimate background seismicity rates in the epidemic-type aftershock sequence model from shallow seismicity data having magnitudes of over 4.5. Then, we perform correlation analysis of the amplitudes of the annual gravity changes and the shallow background seismicity rates, excluding source areas of large earthquakes, and find moderate positive correlation. It implies that annual water movements can activate shallow earthquakes, although the surface load elastostatic stress changes are on the order of or below 1 kPa, as small as a regional case in a previous study. We speculate that periodic stress perturbation is amplified through nonlinear responses of frictional faults.

Research areas: Earthquakes
From Interseismic Deformation With Near‐Repeating Earthquakes to Co‐Seismic Rupture: A Unified View of the 2020 Mw6.8 Sivrice (Elazığ) Eastern Turkey … (2021)

The East Anatolian Fault (EAF) is a left-lateral transform fault accommodating the relative motion between the Anatolian and Arabian plates. On January 24, 2020, M<SUB>w</SUB>6.8 Sivrice (Elazığ) earthquake is the largest event that occurred along the EAF since the nineteenth century. The earthquake provides a unique opportunity to capture a critical stage of the seismic cycle from the interseismic deformation to co-seismic rupture. In this study, we examine the relationship between the interseismic fault activity and co-seismic behavior of the earthquake. A kinematic model of the earthquake obtained from strong-motion, GNSS and teleseismic waveforms along with static displacements from GNSS and InSAR data shows that the mainshock ruptured only 45 km of the 95 km long Sivrice-Pütürge segment. Rupture initiated adjacent to the interseismically weakly coupled northeastern section and propagated unilaterally toward southwest with a rupture velocity of ∼2.5 km/s, stopping ∼30 km before the southwestern segment boundary. The earthquake did not generate any surface offsets. We identified 4 long-term near-repeating earthquake clusters beneath the highest co-seismic slip zone adjacent to the northeastern creeping section. The mainshock was dynamically triggered by a M ∼ 5.4 foreshock located within the zone of near-repeating earthquakes. We suggest that creep along the weakly coupled section of the fault loaded the neighboring locked section leading to the repeating earthquakes below the locked zone. The earthquake partially ruptured a fault segment characterized by high rate of diffuse seismicity, structural complexities and heterogeneous coupling, leading to a source characterized by a complex source time function with relatively slow rupture velocity.

Research areas: Earthquakes