Hello, I am Álvaro González, an Earth scientist who currently works as a research collaborator at the University of Zaragoza (Spain) and as the head of the department of Biology and Geology in a small High School in the Spanish Pyrenees. Below you can find an overview of my research in a diversity of topics. Or you may prefer to browse instead a publication list or research-related news.
The Spanish National Earthquake Catalogue
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. A review of its evolution, precision, and magnitude of completeness aims to help future analyses of the seismicity in the region.
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 this article for a broader audience. The gas storage project was stopped because it might trigger future seismicity, and its facilities are no longer in use.
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, produced a meteor brighter than the Sun, and disintegrated 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). The last forecast maps and results, calculated automatically, can be checked online within the class "one day alarm models". 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 had been 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 calculating the time-dependent probability of the next large earthquake at Parkfield. According to these models, the chance that it will happen in 2017 is about 2.5% (which is lower than the long-term average).
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 episodically. 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. This paper reviews the Fibonacci lattice and shows 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 (available in hard copy under request).