Research

Hello, I am Álvaro González, a postdoctoral natural hazards researcher at the CRM Centre for Mathematical Research (Barcelona, Spain), and guest researcher at the GFZ German Research Centre for Geosciences (Potsdam, Germany).

For my current research, I analyse extensive datasets of hazardous phenomena (mostly earthquakes, but also tropical cyclones, wildfires, karstic collapses, rain events and meteorite impacts) to calculate their frequency, their probability to occur in the future, and the costs and casualties they may eventually cause. This contributes to informed decision-making in disaster risk management, working towards a safer world.

I am a vocational educator, with experience teaching Earth sciences in university and high school levels, and a passionate communicator about natural hazards to non-specialist audiences and the general public.

Below you can find an overview of my research results. Or you may prefer to browse instead a publication list, research-related news, or a virtual library about several earthquakes in Spain.

Size-frequency distributions of hazardous phenomena

Karst sinkholes on the shore of Dead Sea Generally, small events or features in Nature are more frequent than large ones. This observation is statistically described by a size distribution, which specifies how frequent something is as a function of how large it is. We have analysed with a novel technique the size distributions of diverse natural phenomena (earthquakes, karst sinkholes, wildfires, tropical cyclones, rain clusters and meteorite impacts). And also we have explored how to rigorously merge datasets spanning vastly different size ranges. This research line aims to better calculate the long-term hazard of each phenomenon.

Regional seismicity and seismic hazard

Epicentres until December 2013 The Spanish National Earthquake Catalogue is the most complete earthquake database for Spain. It has improved along time, thanks to the development of the seismic network and the upgrades of the routine data acquisition and analysis. My review of its evolution, precision, and magnitude of completeness aimed to help future analyses of the seismicity in the region. I have used this database, merged with those of France, Portugal, Morocco and Algeria, as an input for the official seismic hazard assessment of the Spanish nuclear power plants.

Seismicity triggered by gas injection

In 2013, over a thousand earthquakes, with magnitudes up to 4.3, were recorded in the close vicinity of a platform for underground natural gas storage offshore Spain. We relocated the earthquakes, calculated focal mechanisms and found that the sequence was most likely triggered by a gas injection test. Official reports also reached similar conclusions, as reviewed in my article for a broader audience. The gas storage project was stopped because the scientific consensus was that it might trigger future seismicity.

Active faults and paleoseismicity

In theTaupo Rift (New Zealand), our findings of active faults were took into account for changing the planned site of a new geothermal power station. In the Iberian Range (Spain), we have found active faults which ruptured the ground producing large earthquakes in the last tens of thousands of years. I have contributed digital cartography, references, and data of faults in this Range for the Quaternary Active Faults Database of Iberia (described here) and the European Database of Seismogenic Faults, which have been used for seismic hazard assesments.

Seismic characterization of the Chelyabinsk meteor

On 15 February 2013, a house-sized asteorid entered Earth's atmoshere at 15 kilometres per second, producing a meteor brighter than the Sun, and disintegrating over the Russian region of Chelyabinsk. This resulted in an atmospheric shock wave which destroyed the windows of thousands of buildings, injuring over 1700 people.

The shock wave also shook the ground and the resulting seismic surface waves were recorded at even thousands of kilometres away. We analyzed seismic records and a video of this event, and were able to pinpoint the location of the terminal meteor explosion in the stratosphere.

Collaboratory for the Study of Earthquake Predictability (CSEP)

CSEP is an international initiative for objective, independent testing of earthquake forecasts. The Southern California Earthquake Center is one of its nodes, and it is currently testing models which I submitted for daily probabilistic forecasting of earthquake locations in several regions (California, western Pacific Ocean and worldwide). Given that earthquakes tend to group in space, these maps assign higher spatial probabilities for future earthquakes in the vicinity of previous ones, an idea which I had tested retrospectively for Spain.

Time-dependent earthquake probabilities in the San Andreas Fault

Earthquake probabilities change with time: earthquakes can trigger other ones (such as aftershocks) or, conversely, inhibit others by releasing elastic strains accumulated over long timescales. To account for this in Statistics, the simplest option is a so-called renewal model, in which the probability of the next event depends only on when the last one took place.

The Parkfield section of the San Andreas Fault has generated a well-documented sequence of earthquakes with magnitude about 6. Just after the last one (in 2004) we applied a new renewal model and existing ones to calculate the time-dependent probability of the next large earthquake at Parkfield. According to these models, the chance that it will happen in 2024 is about 6% to 8%.

Education and outreach on earthquakes and tsunamis

I have advocated for educating on natural hazards as a key for reducing population vulnerability. As part of this effort, I wrote an overview on earthquakes and tsunamis for a general audience (in Spanish), and brought into public attention the tsunami hazard on the Spanish coast. Regularly, I deliver seminars about earthquakes and tsunamis at the University of Zaragoza and occasionally talk to the press about the topic.

Forecasts of earthquake casualties and economic costs

For planning and preparedness, it is important to forecast the casualties and economic costs which might result from future earthquakes. We calculated such potential damages for scenario earthquakes in urban areas of Spain. To do so, we considered factors such as population density, public investment per capita and calculated shaking intensity.

Statistical Physics models for earthquake occurrence

Earthquake generation is a complex process in which faults slowly accumulate elastic strain and release it suddenly. Each fault can be regarded as a set of interacting elements which share this elastic loading, and faults in turn interact with each other, dissipating this loading on larger scales. Such processes can be analyzed with models of Statistical Physics, the branch of Science which deals with systems with many interacting parts.

Even a minimalist model of strain loading and unloading of a fault generates complex behaviour. Despite it is stochastic, the largest earthquakes in the model can be forecast to some extent. The forecasts improve if the model is synchronized with others, a procedure which may be eventually applied to models of faults for probabilistic earthquake forecasting.

The spherical Fibonacci lattice

Many numerical computations regarding the Earth's surface require using uniformly spaced sampling points. The spherical Fibonacci lattice is a very uniform spiral pattern of points, based on the golden ratio and inspired in natural patterns with optimal packing. I reviewed the Fibonacci lattice and showed that it can be used to measure areas on the sphere accurately.

Natural analogues of radioactive waste underground disposal

Safe, long-term, disposal of high-level radioactive waste is an unsolved problem. One option is to bury it deep underground within canisters surrounded by barriers. But it is difficult to extrapolate what will happen over millenia in such systems.

A few locations are, to some extent, natural analogues of such disposal sites, and provide evidences of these long-term processes. For example, there are natural fission reactors and uranium deposits preserved at depth by natural means. The Spanish Nuclear Security Council published our synthesis on these natural analogues and an extensive report on the most significant ones).