Inversion and assimilation of geodetic data
Convenors: T. Sagiya (Japan), B. Minster (USA)
Session Overview: Jean-Bernard Minster, UCSD (15 minutes)
In Session 4.1, we will discuss how to incorporate various observations into numerical simulations. Following are the main themes to be discussed:
1. Data assimilation technique used in earthquake simulations:
In order to conduct realistic simulations, we definitely need to incorporate observations into numerical models. Data assimilation is therefore an indispensable part connecting observation and numerical models. The procedure includes updating observables in numerical models, providing constraints on the models, and revising the models themselves. Various kinds of analysis techniques, such as geophysical inversion, simulated annealing, and genetic algorithms, may be used in data assimilation. We will discuss these methods and try to formulate a general framework for the overall problem to be solved. In addition, to improve the ability of simulation models to forecast future crustal activities, data assimilation must be conducted in real time. We will discuss what we can learn from meteorology and oceanography in terms of real time data assimilation.
2. Combination of geodetic observations:
Nowadays various types of geodetic observation are available such as GPS, InSAR, VLBI, SLR, borehole strainmeter, creep meter, etc. Sometimes we also need to incorporate traditional geodetic data that are sparsely sampled in time and perhaps of lesser quality, because these data span a long time period and include precious records of rare seismic events. Each type of observation offers its own advantages so that efficient and optimal combinations of these data are desirable. We will discuss what types of data are necessary in earthquake simulation and how we can combine them.
3. Application of inversion techniques in earthquake simulations:
Inversion technique is an important tool to incorporate various observations into numerical models. Among various inversion techniques, geodetic inversion has a special significance because we have a explicit representation theorem between deformation of the earth and earthquake sources based on dislocation theory. We will discuss usage as well as limitations of inversion techniques in relation to earthquake simulations. We also discuss technical and theoretical development required for the earthquake simulations.
4. Database system for earthquake simulations:
In order to conduct data assimilation in an efficient way, it is essential to have a well-designed database system. Database systems are expected to contain all the information about earth structure, various types of observations, parameters controlling fault friction and failure laws, and so on. In order to be effective, databases should be designed so as to guarantee quick and efficient response to various queries. We will also discuss how to deal with incoming observation data in real time.
Session Plenary: (1 Hour)
David Jackson, UCLA (30 minutes) Geophysical inverse problem (title is tentative) Takeshi Sagiya, GSI (30 minutes) Continuous GPS Array of Japan and its Application to Crustal Activity Modelling
Detailed Session: (2.5 Hours)
1. Data assimilation in earthquake simulations Jean-Bernard Minster and Michael Watkins (10 minutes) Data Assimilation and Options in Earthquake Modeling 2. Combination of different geodetic observations Andrea Donellan, Gregory Lyzenga, Don Argus, Gilles Peltzer, Jay Parker, Fran Webb, Mike Heflin, and James Zumberge (15 minutes) Use of GPS and InSAR technology and its further development in earthquake modelling 3. Application of inversion techniques in earthquake simulations Mitsuhiro Matsu'ura, Akira Nishitani, and Yukitoshi Fukahata (15 minutes) Slip history during one earthquake cycle at the Nankai subduction zone inferred from the inversion analysis of levelling data with a viscoelastic response function Peng Cheng Liu and Ralph Archuleta (15 minutes) Nonlinear Inversion for Earthquake Rupture Parameters 4. Database system for earthquake simulations Akitake Makinouchi (10 minutes) Database system for the Earth Simulator Discussion and comments (1 hour 25 minutes)