Fractal Dimension of Seismicity at Cangar, Arjuno-Welirang Complex, East Java

This study aimed to determine the value of fractal dimensions in the Cangar region, Arjuno-Welirang Volcano Hosted Geothermal System (VHG) based on seismic time series data. The determination of fractal dimension values is done using the delay embedding theorem method. The process starts from determining the value of the delay time by using the autocorrelation function and also determining the value of embedding dimensions using the False Nearest Neighbors (FNN) method. These two parameters are used to reconstruct the attractor diagram. Quantization of the attractor diagram provides a correlation dimension curve that is directly related to the fractal dimension value. The fractal dimension value in the study area tends to be high, ranging from 5.43 to 6.29. This high value is associated with the amount of energy needed by hot water to make their way out to the surface through rock with very little permeability. The emergence of fractures due to the continuous heat discharge process in Cangar hot water and the gas release process triggers the appearance of seismic signals.