O^-1earthquake-like precursors: a MaxEnt-μSR MgO study

Earthquake-like precursor O^-1 effects [1,2] are studied by analyzing Muon-Spin-Resonance (μSR) MgO data using Maximum Entropy (ME). [3,4] MgO is ideal due to its presence in the Earth's crust: O^-1or positive-hole formation results from a 2-stage break-up of an O anion pair under high-T or high-P conditions. [2] As T increases above room temperature (RT) a small O-ion % is predicted to produce an O^-1state.[2] ME analysis of transverse field (TF; 100 Oe) μSR data of a 3N-MgO single crystal show above RT a Gaussian signal at 1.36 MHz and a Lorentzian signal at 1.4 MHz. For similar oxides like MnO, TFμSR show only the μO Gaussian signal, as positive muons probe near negative O ions. [3,4] The extra 1.4-MHz MgO signal indicates the existence of extended O 2p states. [1, 2] Between 200 & 400 °C where O^-1 formation occurs, we find evidence of a missing (3^rd μSR) fraction. The relation of O-valency effects and earthquake-like precursors is discussed. 1] FT Freund, Nat Hazards Earth Sys Sci 7(2007) 1. 2] FT Freund et al, Phys Chem Earth 31(2006) 389. 3] C Boekema and MC Browne, MaxEnt 2008, AIP Conf Proc #1073 p260. 4] S Lee et al, HUIC Educ, Math & Eng Tech Conf, Uo HI (2013).