Detection and estimation of the Slichter mode based on strain observation of the 2010 Chilean earthquake

<p>The Slichter mode (<sub>1</sub>S<sub>1</sub>) is the longest-period mode of the free oscillations of the Earth. The period of the Slichter mode directly depends on density jump between the outer liquid and the inner solid core which makes the detection of this oscillation very important for gaining a more detailed insight into the structure of the Earth’s interior. Reliable empirical data on the detection of Slichter mode are absent, which is associated with the rather low amplitude of this mode on the surface.</p><p>In this work, for the first time, an attempt is made to detect the Slichter mode using the strain data from the largest 2010 Chilean earthquake recorded by the Baksan laser interferometer–strainmeter (Sternberg Astronomical Institute of the Moscow State University (SAI MSU)) with a measuring arm length of 75 m in the Elbrus region, the Northern Caucasus.</p><p>A new asymptotically optimal algorithm for data analysis is developed. The algorithm uses the maximum likelihood method and takes into account the features of the detected signal and the properties of seismic noise. The algorithm is based on the fundamental principles of the theory of optimal signal reception against the background of non-Gaussian noise, which provides the most effective signal detection in accordance with the Neumann-Pearson optimality criterion. Simultaneously with the detection, the degenerate frequency of the mode and splitting parameter <em>b</em> are estimated. Applying the developed algorithm to the strain data of the Chilean earthquake yielded two sets of the most probable candidates for the Slichter mode parameters: <em>T<sub>1</sub></em> = 5.905 h at <em>b<sub>1</sub></em>= 0.1038 and <em>T<sub>2</sub></em> = 6.581 h at <em>b<sub>2</sub></em>= 0.1046. The obtained sets of the Slichter mode parameters have a false-alarm probability of 0.012 and 0.005, respectively.</p><p>The comparison of our results with the theoretical models and the previous results of experimental determinations of the period of the Slichter mode shows a close correspondence of the period <em>T<sub>1</sub></em> = 5.905 h to the period in the CORE11 model (Widmer et al., 1988); the difference is below 1.5%. In the case of the PREM models (Rosat et al., 2006), the obtained periods correspond to the density jumps between the inner and outer cores of <em>Δρ<sub>1</sub></em> = 0.456 g/cm<sup>3</sup> for <em>T<sub>1</sub></em>= 5.905 h and <em>Δρ<sub>2 </sub></em>= 0.360 g/cm<sup>3</sup> for <em>T<sub>2</sub></em> = 6.581 h.</p><p>This work is supported by the MSU Interdisciplinary Scientific and Educational School of Moscow University "Fundamental and Applied Space Research" and the Russian Foundation for Basic Research under Grant No Grant No 19-05-00341.</p>

1960 Chile

The 1960 Chilean earthquake, the largest earthquake in recorded history, ruptured nearly 620 miles of seafloor, generated a tsunami well over 50 ft (15 m) high in Chile, and moved the entire country to the west in a matter of minutes as the ground shook. The tsunami following the earthquake caused Pacific-wide destruction. This chapter charts the progress of the tsunami across the Pacific Ocean, beginning with tsunami survivor stories from Chile and then moving to the Moai of Easter Island, bad decisions in Hawaii, and the unwelcome surprise of this distantly generated event for Japan. This was an ocean-wide disaster that provides important lessons regarding what happened in the past and what will happen in the future.

Natural Disasters and Birth Rate: Evidence from the 2010 Chilean Earthquake

A major natural disaster can generate changes in the affected population’s behavior. As Chile is considered one of the countries with the highest seismic activity and has experienced several of the most intense earthquakes on record in the world, this work seeks to identify behavioral changes in the birth rate within an affected population related to a natural disaster in Chile. Based on evidence from the 2010 Chilean earthquake, an empirical study was carried out drawing on birth rate data and social data associated with earthquakes in Chile between 2004 and 2015. Two models were estimated. The first model is a difference-in-differences model for determining the effect of the disaster on the birth rate in the affected area in the post-disaster period. The second model is a triple-difference model that includes the trend of the data over time. The results indicate a positive relationship between the variation in the birth rate and the occurrence of the natural disaster. Studying the relationship between disaster events and fertility contributes to understanding the phenomena of social dynamics. This knowledge could improve public policy decision making for better planning in the face of a natural disaster.

Maria Graham and the Chilean earthquake of 1822: contextualizing the first female-authored article in Transactions of the Geological Society

This chapter explores the background to the first female-authored article in the Transactions of the Geological Society (published in 1824) and outlines the controversy later caused by the article. The author, Maria Graham (1785–1842), has generally been assumed not to have been a geologist herself, and is therefore often excluded from discussions of women's early contributions to geology. This chapter demonstrates that this was not the case, and that Graham had a strong interest in geology and some competence in the discipline. It further situates Graham in a flourishing culture of early nineteenth-century ‘polite science’, and argues that the episode, when parsed correctly, demonstrates the perhaps surprising extent to which women were able to participate in contemporary geological enquiry and debate, even as they undoubtedly laboured under considerable disadvantages compared with their male counterparts.