Steelmaking is a key-sector for development; it is also one of the most energy and CO2 intensive industries. Brazilian steelmaking was responsible for 44.3 million metric tons of CO2 emissions and 40% of its output supported the international steel demand in 2018. Then, there is a need to harmonize the increasing steel demand with low carbon energy alternatives towards sustainable development. Here, we forecast scenarios until 2050 to analyze the CO2 reduction potential through energy transitions in two production routes of the Brazilian steelmaking: for primary steel, the increase of renewable charcoal use in blast furnaces; and for secondary steel, whose direct emission is relatively low but it is highly power intensive, the use of on-site photovoltaic (PV) energy to meet the power demand. Renewable energy sources for electricity play a particularly relevant role as power demand increases 69% with the substitution of charcoal for coke. The analysis has been supported by econometric models and emission factors from the IPCC GHG inventory guidelines for direct and indirect emissions. Results have shown that steel production will increase 1.8% per year from 2020 levels and will yield 77MtCO2 in 2050. The Charcoal+PV scenario can mitigate 49% of such emissions. The land-intensity to enable such scenario is 51m² per avoided tCO2 for the entire period. Alternatively, if steel sector’s emissions were compensated by native reforestation, this value decreases to 38m²/tCO2. However, according to the uncertainty analysis, reforestation presents a higher land-intensity than charcoal+PV scenario in 31% of the Monte Carlo simulations. In addition, other issues affect suitability of the scenarios and must be discussed: the benefit-cost of bioenergy versus costs of conservational reforestation; ancillary benefits of standing forests such as biodiversity improvement. Moreover, considering the carbon cycle, charcoal is sustainable far beyond the analyzed period, whereas new areas will be needed to stock carbon in conservational reforestation projects. The findings of this study can assist governmental and private decision-makers to elaborate policies for more plausible pathways to confront climate change and guarantee economic, social, and environmental development.

We present interannual to decadal glacier and geomorphic change measurements at multiple sites across Western North America from the 1950s until present. Glacierized study sites differ in terms of glacial geometry and climatology, from continental mountains (e.g., Glacier National Park) to maritime stratovolcanoes (e.g., Mt. Rainier). Quantitative measurements of glacier and land surface change are obtained using the Historical Structure from Motion (HSfM) package. The automated HSfM processing pipeline can derive high-resolution (0.5-2.0 m) Digital Elevation Models (DEMs) and orthomosaics from historical aerial photography, without manual ground control point selection. All DEMs are co-registered to modern airborne lidar and commercial satellite stereo reference DEMs to accurately measure geodetic surface elevation change and uncertainty. We use scanned historical images from the USGS North American Glacier Aerial Photography (NAGAP) archive and other aerial photography campaigns from the USGS EROS Aerial Photo Single Frames archive. We examine the impact of regional climate forcing on glacier volume change and dynamics using downscaled climate reanalysis products. By augmenting the record of quantitative glacier change measurements and better understanding the relationship between climate forcing and heterogeneous glacier response patterns, we aim to improve our understanding of regional glacier mass change, as well as inform management decisions impacting downstream water resources, ecosystem management, and geohazard risks.

The twin pressures to achieve mind-share and to harness available computing power drive the evolution of geoscientific data analysis tools. Such tools have enabled a remarkable progression in the atomic or fundamental unit of data they can easily analyze. In the mid-1980s we analyzed one or a few naked arrays at at time, and now researchers routinely intercompare climatological ensembles each comprising thousands of files of heterogeneous variables richly dressed in metadata. Two complementary semantic trends have empowered this analytical revolution: more intuitive and concise analysis commands that can exploit more standardized and brokered self-describing data stores. This talk highlights how tool developers can leverage these trends to successfully imagine and build the analysis tools of tomorrow by understanding the needs of domain researchers and the power of domain specific languages today. This talk will also highlight recent improvements in compression speed and interoperability that geoscientists can exploit to reduce our carbon footprint. Observations and simulations to advance Earth system sciences generate exabytes of archived data per year. Storage accounts for about 40% of datacenter power consumption, with its attendant consequences for greenhouse gas emissions and environmental sustainability. Precision-preserving lossy compression can further reduce the size of losslessly compressed data by 10-25% without compromising its scientific content. Modern lossless codecs (e.g., Zstandard or Zlib-ng) accelerate compression and decompression, relative to the traditional Zlib, by factors of 2-5x with no penalty in compression ratio. These proven modern compression technologies can help geoscientific datacenters become significantly greener.

Chemical gardens are self-assembled tubular structures formed via abiotic precipitation upon the interaction of metal-ion salts with aqueous solutions of anionic species such as silicate, carbonate, or phosphate. These tubular structures have been suggested to be relevant for the early Earth and Earth-like planets and moons where alkaline silica and carbonate rich soda oceans are thought to be widespread. Carbonate and silica gardens are believed to be forming under the geochemical conditions of these soda oceans. Silica gardens are self-compartmentalized compositionally distinct bilayered mineral membranes. These membranes are small batteries that selectively catalyze the synthesis of prebiotically relevant organic compounds such as carboxylic acids, amino acids, and nucleobases by condensation of formamide. Recently, we have grown chemical gardens and mineral vesicles by immersing different metal salts in soda lake water and inferred that mineral self-organization could be a plausible scenario on soda oceans of early Earth and extraterrestrial planets and moons such as Enceladus. In this work, we have performed in-situ monitoring of the chemical gradient, pH and electrochemical potential differences across macroscopic calcium carbonate tubular structures grown by immersing calcium chloride salt pellets in carbonate-rich soda lake water (Lake Magadi, Southern Kenyan Rift Valley). To understand the temporal evolution of the growth process, we have performed ex-situ X-ray diffraction, Raman and infrared spectroscopy, and scanning electron microscopy of the tubular structures isolated after different periods of growth. We have also compared our results with calcium carbonate and silica gardens grown in model laboratory solutions. The walls of calcium carbonate tubular structures are composed of bilayers of texturally different but mineralogically similar crystalline calcite. We have observed that pH gradients across these “natural” calcium carbonate tubes are comparable to that of silica gardens and higher than that of synthetic carbonate gardens. We have discussed the implications of the texture, ionic gradient, pH and electrochemical potential differences across the tubes to material sciences, prebiotic chemistry, and origin of life.

Micromagnetic Tomography (MMT) is a technique that combines X-ray micro tomography and scanning magnetometry data to numerically invert the surface magnetic signal for the magnetic potential of individual magnetic grains via their spherical harmonic expansion [1]. The dipole and higher order multipole moment solutions are uniquely determined, which has been proved in [2]. As a result, this method has allowed to analyze the signal of individual grains in rock samples and synthetic samples, thus providing a new pathway to study the rock magnetic properties of the remanent magnetization carriers [3]. Furthermore, the higher order multipole signals in the magnetic particles are an indication that the grains carry more complex magnetic orderings, such as multi-domain or vortex states. Therefore, these higher order moments can be used to constrain the magnetic configuration of the magnetic particles. In this work we review the multipole expansion method used by MMT. In addition, we show three dimensional micromagnetic modelling results to predict the multipole signal of magnetic particles in different local energy minimum magnetization states. We show that for certain grains it is possible to uniquely infer the magnetic configuration from the inverted magnetic multipole moments. This result is crucial to discriminate single-domain particles from grains in more complex configurations. Our investigation proves the feasibility to statistically select ensembles of magnetic grains with similar properties, such as the magnetic state, which is a step forward to find stable paleomagnetic recorders. [1] L. V. de Groot, K. Fabian, A. Béguin, P. Reith, A. Barnhoorn and H. Hilgenkamp. Determining Individual Particle Magnetizations in Assemblages of Micrograins. Geophysical Research Letters, 45(7):2995–3000, 2018. [2] K. Fabian and L. V. de Groot. A uniqueness theorem for tomography-assisted potential-field inversion. Geophysical Journal International, 216(2):760–766, 2018. [3] D. Cortés‐Ortuño, K. Fabian and L. V. De Groot. Single particle multipole expansions from Micromagnetic Tomography. Geochemistry, Geophysics, Geosystems, 22:e2021GC009663, 2021.

A circularly polarized, large-amplitude Alfvén wave in a plasma with finite plasma ß becomes parametrically unstable under specific plasma conditions, in which the pump wave will decay into several daughter waves with different wavenumbers and frequencies. Magnetohydrodynamic simulations have been conducted to investigate the evolution of the parametric decay process, using the MRCv3 code. This code is based on the computational library libMRC, which provides a number of numerical methods that solve MHD and extended-MHD models. For the MRCv3 simulations, a uniform Cartesian grid with periodic boundary conditions is used, with the assumptions of no background flow and a uniform background plasma density ρ and magnetic field B0. Results from these simulations will be presented, discussed, and compared to previous numerical and analytic results.

Oscillating Water Column (OWC) systems are an iteration of terminator ocean energy technology which generate electrical energy from turbine torque induced by the compression of air in a chamber from changing water level height. OWC systems are a well-established technology, however, there have been no studies to date which quantify the life cycle environmental impacts of these systems in a geographic context. The goal of this study is to optimally size an OWC system for selected coastline sites along the eastern New England, USA coast and then assess the environmental impacts of the varying system sizes. An OWC system is optimally sized when the volume of its concrete chamber is scaled proportionally to its generation potential; maximizing electrical energy output while minimizing chamber material consumption. Therefore, geospatial variability in generation potential will affect optimized chamber size, in turn, varying the chamber material consumption. Environmental impacts of the systems were assessed via their contribution to global warming potential due to emissions released at every phase within the life cycle system boundaries from mineral extraction to electricity generation using life cycle assessment (LCA). The functional unit used for the LCA was 1 kWh. A radial geospatial interpolation of wave power and wave period measurements from five Integrated Ocean Observing System buoys was integrated from 2003 to 2017 using monthly timesteps to estimate the coastal generation potential of each OWC system. A sample size of 6,775 shoreline sites returned average generation potentials ranging from a maximum of 6.24 kW m^-1 of wave crest for every 100 km of coastal length to a minimum of 0.31 kW m^-1 of wave crest for every 100 km of coastal length. This study revealed high variability in estimated energy generation potential over a short geographical span and, therefore, high variability in chamber material consumption between 115.08 m^3 - 2132.33 m^3 of concrete. These findings emphasize the necessity of quantifying the life cycle climate change impacts of OWC installations prior to design at a national level, as they vary geographically and are influenced by the optimal chamber size and wave power potential.

Although it has been well recognized that clouds tremendously affect the surface solar irradiance and its direct and diffuse partitions, accurately forecasting solar radiation in cloudy conditions remains a major challenge. This study focuses on two aspects of the challenge: impacts of cloud microphysics and model domain size. First, we will examine the sensitivity of surface solar radiation and its partitions to cloud microphysics by using the state of art Weather Research and Forecasting model specifically designed for simulating and forecasting solar radiation (WRF-Solar). A number of microphysical schemes will be tested, and comparison against the measurements of shallow cumulus clouds and stratiform clouds selected at the DOE ARM SGP Site. Efforts will be made to quantify the resultant uncertainty spread. Second, identifying the physical causes of the underlying model differences is even more challenging. To address this, we will introduce a new model evaluation framework based on different setups of WRF-Solar (single column, LES, and nested WRF). In particular, we will examine the effect of the number of LES grid columns and its lower limit producing reasonable results. Commonly used evaluation metrics will be used in our model evaluation, including the used RMSE, MAE, MAPE, and relative Euclidean distance. The results will provide physical insight into the understanding of cloud-radiation interactions and forecasting of solar radiation in cloudy conditions.

Abstract: In climate-ocean models, eddy mixing coefficients are often constant in space and time. However, observations, advances in theory, and high-resolution-eddy-resolving ocean models have revealed significant variability in the strength of isopycnal mixing both spatially and temporally. A theory that includes the effect of mean flow suppression has been developed by [1] it has a strong impact on tracer uptake and ventilation. This theory is used in offline calculations by [1, 2, 4] but has not been implemented as a parameterization in an ocean model and in this study we implement it for the first time in an ocean model [3]. The parameterization is tested in a non-eddy-resolving ocean model, demonstrating passive ventilation of a tracer as a function of depth and latitude. The first main result is this parameterization improves the mean state of the ocean. The other result is this parameterization improves the sensitivity of tracer uptake to changing winds.

The conservation of historic cultural heritage sites is an endeavor that often brings together a diverse group of methods and interests. Castelul Corvinilor, also called Corvin’s Castle or Hunedoara Castle, in central Transylvania (Hunedoara county, Romania) is no exception. The first stone fortification of the medieval castle can be dated to the 14th century and has undergone significant expansion since the original structure was completed. The main building campaigns started in 1440 with the conversion of the fortress into a castle, followed by two more major campaigns during the 17th and 19th centuries, including restoration and remodeling of the original areas. The castle’s historical significance and touristic value make conservation an important goal for the site. This area has been the subject of limited and opportunistic (salvage) archaeological investigations, hoping to understand earlier phases of an administrative complex in the courtyard. However, the excavations did not establish a complete stratigraphy. A ground penetrating radar survey over most of the courtyard was conducted with a 500 MHz antenna, including the main courtyard area. This GPR survey of the courtyard was able to confirm some results of the archaeological excavation and located additional structures which were previously unknown. This presentation included analysis and interpretation of the data in both radargrams and depth slices. They reveal further horizons which indicate bedrock and possible reflections from structures dating to even earlier phases of the site.

Policymakers are trying to cut carbon-dioxide emissions and have promoted generating electricity using solar, wind, wave converters and tidal turbines. But a larger need is to supplement petroleum, the polluting but superb transportation fuel. Ocean Thermal Energy Conversion plants operated during the past 40 years show that OTEC plants have the (1) reliability and (2) massive scale to synthesize a sustainable new global fuel to replace dwindling petroleum supplies. For reliability, we will review the experience of the two OTEC plants currently operating in Japan and Hawai’i. Both plants have demonstrated robust performance for heat exchangers and power components. This record is possible because OTEC uses components similar to typical power plant or air-conditioning machinery. Mini-OTEC generated the first net power in 1978, and it was designed and built in only a year. Today’s onshore plants easily synchronize with the grid frequency, and generate dispatchable electric power instead of the intermittent power from most renewable energy sources. Recent OTEC floating designs benefit from the offshore industry’s hull and power cable research & development. For scale, large OTEC plants operating on the tropical high seas are a feasible supply chain to make transportation fuel in globally-significant volumes. Two recent computer studies suggest that industrial OTEC will have benign biological and climate impact. In comparison, it would require 100% of the US corn harvest to furnish only 30% of US gasoline needs – with no jet fuel or diesel. The expensive drama of obtaining permits for renewable energy projects show that the land and shoreline are already crowded, yet the solar energy equivalent to seven offshore Sahara Deserts is being ignored. Finally, policies and costs supporting or hindering OTEC will be compared for eight nations and the United States, including findings by the International Energy Agency’s Ocean Energy Systems committee. These results explain the current state of this attractive ocean energy resource.

Throughout Earth history, extensive, sub-aerial, basaltic lava flows associated with continental rifting and hot spots have been contemporaneous with major global warming—the more extensive the flows, the longer the period of eruption, and the greater the warming of air and oceans. Around 251 Ma, basalts covered an area in Siberia of 5 million km2 probably within 670,000 years, causing equatorial oceans to become highly acidic with temperatures >40°C. Approximately 96% of all marine species and 70% of all terrestrial vertebrate species went extinct in an environmental crisis mapped globally as the end of the Paleozoic. The Deccan basalts covered an area of 0.5 million km2 around 66 Ma causing warming and extinctions that formed the end of the Mesozoic. Around 56 Ma, rifting of Norway from Greenland extruded as much basalt as 3000 km3 per km of rift per million years, forming the Paleocene Eocene Thermal Maximum. Hundreds of smaller basalt eruptions punctuate the geologic time scale ending geologic eras, periods, epochs, and even ages. In historic time, the Great Þjórsá Lava, covering 970 km2 of Iceland, led to major warming around 8600 BP. The King’s Bowl and Wapi lava fields covered 700 km2 of the Snake River Plain in southern Idaho around 2250 BP during the Roman Warm Period. The basaltic volcano Eldgjá covered 800 km2 of Iceland around 939 AD, associated with the Medieval Warm Period. The much smaller volcano Bárðarbunga erupted 85 km2 of basalt in 6 months starting in 2014, the largest basalt flow since 1783, contemporaneous with sudden warming in the northern hemisphere of 0.47oC from 2014 to 2016. The rate of flood-basalt areal coverage was 0.5 km2 per day. The Kona eruption has been extruding basalts covering 0.6 to 0.4 km2 per day from May 3 through July 27. If this eruption continues for 6 months, it could affect climate as much as Bárðarbunga. Warming appears caused by ozone depletion, allowing more UV-B than usual to reach Earth. UV-B radiation is hot enough to burn skin and is 48 times hotter than infrared radiation absorbed strongly by CO2. Basaltic eruptions emit especially high volumes of chlorine and bromine, which are observed to cause ozone depletion. The exact chemical path is not yet well understood. Heat waves during the summer of 2018 are associated with a “sharply kinked” jet stream often thought caused by ozone depletion.

Better understanding of the hydrological cycle of the Lower Mekong River Basin (LMRB) and addressing the value-added information of using remote sensing data on the spatial variability of soil moisture over the Mekong Basin is the objective of this work. In this work, we present the development and assessment of the LMRB (drainage area of 495,000 km2) Soil and Water Assessment Tool (SWAT). The coupled model framework presented is part of SERVIR, a joint capacity building venture between NASA and the U.S. Agency for International Development, providing state-of-the-art, satellite-based earth monitoring, imaging and mapping data, geospatial information, predictive models, and science applications to improve environmental decision-making among multiple developing nations. The developed LMRB SWAT model enables the integration of satellite-based daily gridded precipitation, air temperature, digital elevation model, soil texture, and land cover and land use data to drive SWAT model simulations over the Lower Mekong River Basin. The LMRB SWAT model driven by remote sensing climate data was calibrated and verified with observed runoff data at the watershed outlet as well as at multiple sites along the main river course. Another LMRB SWAT model set driven by in-situ climate observations was also calibrated and verified to streamflow data. Simulated soil moisture estimates from the two models were then examined and compared to a downscaled Soil Moisture Active Passive Sensor (SMAP) 36 km radiometer products. Results from this work present a framework for improving SWAT performance by utilizing a downscaled SMAP soil moisture products used for model calibration and validation.

Slow downward movements of slope due to long term influence of gravity and physical environment are becoming a slope creep and intentionally towards the high risk ground movement area. We identify the creeping slopes in Ciloto, the prone landslide area in Indonesia using the advanced InSAR technique. Slowly Decorrelated Phase Filter is chosen as the processing multi-temporal method because the number of scatter candidates are greater than single master persistent scatter (PS) technique considering to rural and agriculture tested areas. A partial tropospheric propagation delay has been reduced as well in term of the phase-based power law correction on each interferogram. The InSAR displacement results are describing a very slow motion which might be no surface geomorphic evidence at the site but result in tilt of poles, slump and crack of structures and roads, or abnormal curvature of trees. We use two independent InSAR observations and aspect information determined by digital elevation model (DEM) assuming that the motion’s direction is going to the downward slope. The least square inversion model takes into account for each selected merging ascending and descending scatters to derive 3D vectors; vertical, east-west and north-south components. The firstly two of them are defined based on SAR geometry line of sight looking both from ascending and descending. Since the north-south vector is the most insensitive of slant-range deformation, we assume the horizontal motion owning a projected relationship to slope direction. The result is then simulated to the vertical surface model and horizontal vector displacement on two active zones, Puncak Pass and Puncak Highway Landslides. Considering to two successive Puncak Pass Landslides occurred in February and March 2018, we construct the pre-event history from 2014 to 2017 and locate the zone of depletion and accumulation with the slope creep displacement of 1-2 cm/year. The vertical moves faster than the horizontal at the head scarp while it shows otherwise on the foot body.

The extent to which tropospheric aerosols impact the environment, particularly with regard to climate and human health, remains quite uncertain. Given their proximity to Earth's surface, such particles are likely to contain mixtures of organic and inorganic materials. In addition, they are likely to take on different shapes and have different phases. Reducing the uncertainties in the role these particles play requires detailed knowledge of the chemical and physical properties of the materials they are made from. This work focuses on the retrieval of mid-infrared complex refractive indices from the aerosol extinction spectra of commercially available motor oils. There is reason to believe that motor oils could contribute organic material to tropospheric particles, especially in urban areas with high concentrations of internal combustion processes. Refractive index data for these systems can be used in remote sensing applications to measure, amongst other things, composition and particle size. The motor oil results will be compared to refractive indices of long-chain hydrocarbons recently measured in the laboratory. The image shown is a complex refractive index set for a 5W-20 motor oil taken across the mid-infrared.

Under the impact of global warming and climate change, the frequency of extreme precipitation and drought events have been increasing. In Taiwan, the government usually guides agricultural fallows to meet the needs of domestic, public, and industrial water during droughts. However, this situation causes that the cultivation rights of farmers are not guaranteed even though the priority of agricultural water is higher than that of industrial water. To this end, a framework of virtual water trading market is proposed in this study to protect the cultivation right. The water supply system and field water balance models that use the historical drought event during 2003 to 2004 as the hydrological scenario have been completed to support the gaming water-trading auction. Through the gaming simulation process, agricultural or industrial stakeholders are invited to carry on the round-designed water trading. Based on the results of player's decisions, we discuss the feasibility of water market in this region and investigate the possibility of adopting the water market as a solution of the water reallocation during times of drought. An application with the principle of user charge in the Taoyuan region of Taiwan is successfully implemented. The results show that industrial stakeholders are willing to pay more costs of water purchase to prevent severe loss of production line shutdown caused by water shortage. After several times of the gaming auction, stakeholders may learn the trading information in terms of evaluating the price of water and estimating the possible amount of water. This study can further provide a potential substitute solution to the government and policy makers when the water reallocation is considered during drought periods.

After the recent large earthquake disasters, Japan now emphasizes the role of universities in disaster prevention. Universities with expert knowledge of disasters and prevention are possibly able to play the role of linking the administration and citizens and supporting the collaboration of the many related agencies. Based on this recognition, since 2016, Nagoya University has actively built a framework for collaborating with the National University of Mongolia (MUIS) and the National Emergency Agency of Mongolia (NEMA). Nagoya University and the Open University of Japan intend to share Japan’s experience on “how to raise citizen’s disaster resilience” from the perspective of these universities. After the 1995 Kobe Earthquake, Japan has implemented many earthquake disaster prevention initiatives; however, in 2011, the Great East Japan Earthquake again caused substantial destructive damage. Although adequate measures had been taken, there is still a limit to governmental measures to deal with huge earthquakes with low occurring frequency. In countries where large earthquakes are possible, it is essential for each citizen to strengthen their own buildings or to endeavor to live in a place with good ground conditions and to ensure that this becomes the normal way of life. However, interest in disaster prevention often dissipates, and we are liable to repeat the same mistakes. How can we enhance citizens’ disaster resilience? As emphasized in the Sendai framework, one of the most important factors is “cooperation” and universities could become the focal point of this cooperation. Since 2002, Nagoya University, together with the administration and citizens, has begun to conduct various disaster prevention education projects in Japan. We introduce here the three projects based on Geography, Cultural Anthropology and Environmental Sciences, which were conducted within the period between 2014 and 2018. 1) Establishment of a Cooperative Center for Resilience Research (CCRR) between the National University of Mongolia and Nagoya University. 2) Organizing a public symposium for earthquake prevention by the Mongolian Government and CCRR. 3) Initiating the Grass-roots Joint Project: “Disaster Awareness Enlightenment Project for Large-scale Natural Disasters Caused by Global Environmental Change in Khovd Province, Mongolia” supported by Japan International Cooperation Agency (JICA). Through these projects, we want to determine disaster prevention methods suitable for Mongolia rather than just utilize Japanese methods of disaster prevention.

The earthquake cycle of stress accumulation and release is associated with the elastic rebound hypothesis proposed by H.F. Reid following the M7.9 San Francisco earthquake of 1906. However, observing details of the actual values of time- and space-dependent tectonic stress is not possible at the present time. In previous research, we have proposed two methods to image the earthquake cycle in California by means of proxy variables. These variables are based on correlations in patterns of small earthquakes that occur nearly continuously in time. One of these is based on the construction of a time series by the unsupervised detection of small earthquake clusters. The other is based on expanding earthquake seismicity in PCA-derived patterns, to construct a weighted correlation time series. The purpose of the present research is to compare these two methods by evaluating their information content using decision thresholds and Receiver Operating Characteristic methods together with Shannon information entropy. Using seismic data from 1940 to present in California, we find that both methods provide nearly equivalent information on the rise and fall of earthquake correlations associated with major earthquakes in the region. We conclude that the resulting time series can be viewed as proxies for the cycle of stress accumulation and release associated with major tectonic activity. The figure shows the PCA patterns of small earthquakes associated with 5 major M>7 earthquakes in California since 1950.