Margarita Segou

Margarita Segou
British Geological Survey · Earthquake Seismology

PhD

About

39
Publications
7,299
Reads
How we measure 'reads'
A 'read' is counted each time someone views a publication summary (such as the title, abstract, and list of authors), clicks on a figure, or views or downloads the full-text. Learn more
578
Citations
Introduction
My research aims in improving our understanding behind the physical processes of earthquake nucleation and aftershock triggering in high seismic hazard regions and subduction zones around the world. My work focuses on the development of operational earthquake forecast models that integrate physics and laboratory laws on the existing empirical models.
Additional affiliations
February 2015 - April 2015
The Institute of Statistical Mathematics
Position
  • Visiting Researcher
February 2015 - April 2015
The Institute of Statistical Mathematics
Position
  • Visiting Researcher
September 2012 - September 2014
French National Centre for Scientific Research
Position
  • Henri Poincare Fellow
Description
  • I am a Henri-Poincare fellow for the Observatoire de la Cote d'Azur, focusing on earthquake forecasting in slowly-stressed environments.

Publications

Publications (39)
Article
The development of robust forecasts of human-induced seismicity is highly desirable to mitigate the effects of disturbing or damaging earthquakes. We assess the performance of a well-established statistical model, the epidemic-type aftershock sequence (ETAS) model, with a catalog of ∼93;000 microearthquakes observed at the Preston New Road (PNR, Un...
Article
Full-text available
The 2016–17 central Italy earthquake sequence began with the first mainshock near the town of Amatrice on August 24 (MW 6.0), and was followed by two subsequent large events near Visso on October 26 (MW 5.9) and Norcia on October 30 (MW 6.5), plus a cluster of 4 events with MW > 5.0 within few hours on January 18, 2017. The affected area had been m...
Article
Full-text available
Operational earthquake forecasting protocols commonly use statistical models for their recognized ease of implementation and robustness in describing the short-term spatiotemporal patterns of triggered seismicity. However, recent advances on physics-based aftershock forecasting reveal comparable performance to the standard statistical counterparts...
Article
Earthquakes occur as the result of long-term strain accumulation on active faults and complex transient triggering mechanisms. Although laboratory experiments show accelerating deformation patterns before failure conditions are met, imaging similar preparatory phases in nature remains difficult because it requires dense monitoring in advance. The 2...
Article
Full-text available
The M7.1 2018 Anchorage earthquake occurred in the bending part of the subducting North Pacific plate near the geometrical barrier formed by the underthrusting Yakutat terrane. We calculate the triggering potential related with stress redistribution from deformation sources including the M9.2 1964 earthquake coseismic slip, postseismic deformation,...
Article
Full-text available
Coseismic stress changes have been the primary physical principle used to explain aftershocks and triggered earthquakes. However, this method does not adequately forecast earthquake rates and diverse rupture populations when subjected to formal testing. We show that earthquake forecasts can be impaired by assumptions made in physics-based models su...
Article
Full-text available
The 2016–2017 Central Apennines earthquake sequence is a recent example of how damages from subsequent aftershocks can exceed those caused by the initial mainshock. Recent studies reveal that physics‐based aftershock forecasts present comparable skills to their statistical counterparts, but their performance remains a controversial subject. Here we...
Article
The 2016-2017 Central Italy seismic sequence ruptured overlapping normal faults of the Apennines mountain chain, in nine earthquakes with magnitude Mw > 5 within a few months. Here we investigate the structure of the fault system using an extensive aftershock data set, from joint permanent and temporary seismic networks, and 3-D Vp and Vp/Vs veloci...
Article
Full-text available
The Manassi section in Levkas Island belongs to the Pre-Apulian (Paxos) zone, the most external domain of the Hellenic realm. Its Early Tortonian sediments contain a rich foraminiferal fauna dominated, in numbers of individuals, by planktic species. Its benthic foraminiferal assemblage is characterized by a high number of taxa, with low numbers of...
Article
Full-text available
The neotectonic graben of Corinth gulf forms an interesting case study from the geodynamical and seismological point of view, since specific characteristics met on the fault zones around the gulf and the adjacent seismological data pose several questions related with the overall modern activity across a number of neotectonic faults. Indexing active...
Article
Full-text available
The M=8.1 Chiapas and the M=7.1 Puebla earthquakes occurred in the bending part of the subducting Cocos plate 11 days and ~600 km apart, a range that puts them well outside the typical aftershock zone. We find this to be a relatively common occurrence in Mexico, with 14% of M>7.0 earthquakes since 1900 striking more than 300 km apart and within a 2...
Article
Full-text available
At 01:36 UTC (03:36 local time) on August 24th 2016, an earthquake Mw 6.0 struck an extensive sector of the central Apennines (coordinates: latitude 42.70° N, longitude 13.23° E, 8.0 km depth). The earthquake caused about 300 casualties and severe damage to the historical buildings and economic activity in an area located near the borders of the Um...
Article
Full-text available
When a major earthquake strikes, the resulting devastation can be compounded or even exceeded by the subsequent cascade of triggered seismicity. As the Nepalese recover from the 25 April 2015 shock, knowledge of what comes next is essential. We calculate the redistribution of crustal stresses and implied earthquake probabilities for different perio...
Article
I perform a retrospective forecast experiment in the most rapid extensive continental rift worldwide, the western Corinth Gulf (wCG, Greece), aiming to predict shallow seismicity (depth <15 km) with magnitude M ≥ 3.0 for the time period between 1995 and 2013. I compare two short-term earthquake clustering models, based on epidemic-type aftershock s...
Article
Full-text available
At 01:36 UTC (03:36 local time) on August 24th 2016, an earthquake Mw 6.0 struck an extensive sector of the central Apennines (coordinates: latitude 42.70° N, longitude 13.23° E, 8.0 km depth). The earthquake caused about 300 casualties and severe damage to the historical buildings and economic activity in an area located near the borders of the Um...
Article
Full-text available
We calculate stress changes resulting from the M = 6.0 West Napa earthquake on north San Francisco Bay area faults. The earthquake ruptured within a series of long faults that pose significant hazard to the Bay area, and we are thus concerned with potential increases in the probability of a large earthquake through stress transfer. We conduct this...
Article
Full-text available
We investigate the interaction between transform faults and normal faults in western Greece, based on seismological analysis and static stress transfer calculations associated with the 8 June 2008 Mw=6.4 Achaia earthquake. We present a relocated earthquake catalog for the period between June 2008-January 2010, when two normal faulting events on 18...
Article
Full-text available
Mainshocks are calculated to cast stress shadows across broad areas where aftershocks occur. Thus a key problem with stress-based operational forecasts is that they can badly underestimate aftershock occurrence in the shadows. We examine the performance of two physics-based earthquake forecast models (CRS) based on Coulomb stress changes and a rate...
Article
Full-text available
Mainshocks are calculated to cast stress shadows across broad areas where aftershocks occur. Thus a key problem with stress-based operational forecasts is that they can badly underestimate aftershock occurrence in the shadows. We examine the performance of two physics-based earthquake forecast models (CRS) based on Coulomb stress changes and a rate...
Article
Full-text available
The aftershock zone of each large (M≥7) earthquake extends throughout the shallows of planet Earth. Most aftershocks cluster near the mainshock rupture, but earthquakes send out shivers in the form of seismic waves, and these temporary distortions are large enough to trigger other earthquakes at global range. The aftershocks that happen at great di...
Article
Full-text available
Immediately after the 12 May 2008 M 7.9 Wenchuan earthquake, we began calculating the static stress change on major faults surrounding the rupture zone (Parsons et al. , 2008), and Toda et al. (2008) mapped out regional Coulomb stress changes (Fig. 1). The purpose was twofold: (1) to identify the most likely locations (stress increases) of dangerou...
Article
Full-text available
[1] We perform a retrospective forecast test using Northern California seismicity for the period between 1980 and 2009. We compare 7 realizations of the short-term clustering epidemic-type aftershock sequence (ETAS) model, and 21 models combining Coulomb stress change calculations and Rate/State theory (CRS) to forecast seismicity rates in 10 day t...
Article
Full-text available
The Seismic Hazard Harmonization in Europe (SHARE) project, which began in June 2009, aims at establishing new standards for prob-abilistic seismic hazard assessment in the Euro-Mediterranean region. In this context, a logic tree for ground-motion prediction in Europe has been constructed. Ground-motion prediction equations (GMPEs) and weights have...
Article
Full-text available
In recent years stochastic optimization has become popular in modeling highly complex natural systems as opposed to traditional approaches, such as regression analysis. This paper tests the efficiency of regression analysis over mathematical optimization by evaluating the performance of stochastic (genetic algorithms, simulated annealing) and deter...
Article
Full-text available
We have calculated Coulomb stress changes between 1980-2006 in Northern California from fourteen events as well as from the major historic ruptures of 1865, 1868 and 1906. The seismic and fault geometry parameters are taken from the Working Group on California Earthquake Probabilities report (2008). We assess the static Coulomb stress hypothesis as...
Article
The M 7.1 Darfield earthquake occurred 40 km west of Christchurch (New Zealand) on 4 September 2010. Six months after, the city was struck again with an M 6.2 event on 22 February local time (21 February UTC). These events resulted in significant damage to infrastructure in the city and its suburbs. The purpose of this study is to evaluate the perf...
Article
Strong motion records are the original input data for earthquake engineering studies and earthquake resistant building codes. Records originating from both, analogue and modern digital instruments should be subjected to processing in order to derive credible engineering parameters, such as spectral ordinates. A number of processing procedures have...
Article
Full-text available
Ground motion prediction equations, widely known as attenuation relations, are common input for probabilistic and deterministic seismic hazard studies. The construction of a ground motion model to describe such a complex phenomenon as the effects of seismic wave propagation is highly dependable on a number of parameters. The quality and the distrib...
Article
Full-text available
On August 14, 2003 a strong earthquake (Mw 6.4) stroke the island of Lefkada. The epicenter was located off shore, about 30 km WNW of the town of Lefkada. A significant number of earthquake-related phenomena such as ground fissures, landslides, rockfalls, soil liquefaction and coastline changes were observed. Moderate damages due to geotechnical ev...
Conference Paper
Full-text available
The present paper focus on the rectification of QuickBird imagery (Standard PSM True Color image) in order to update the urban planning of Parikia (Paros island, Greece). Although the spatial resolution is sufficient for such application and the radiometric information is often better than the case of existing aerial photos, an accurate geometrical...

Projects

Projects (2)
Project
Understanding how earthquakes interact at long distances
Project
Provide preliminary earthquake forecasts for the unfolding sequence in the Central Apennines that started last August.