Self-potential (SP) is a signal from an electric field produced by natural sources in the subsoil and is measured as the voltage difference between two points on the earth's surface as function of time as well as distance. Recently, it has been shown that the "power-law" behavior of SP time series can better be determined by the procedures based on the assumption of self-affinity. Detrended Fluctuation Analysis (DFA) is a statistical tool developed to determine self-affinity properties of stochastic and chaotic signals, which are either stationary or nonstationary over time. In this work, a SP monitoring station located near Gülbahçe village of Urla town and the daily time series data of SP and subsoil temperatures recorded for two years are described. The numerical results of DFA yielded fluctuation exponents near 1,5 indicated that the SP process recorded at Urla Station is a quite possibly from a nonstationary process. This result is also cross-validated considering the fact that estimate of spectral power β at low frequencies was nearly 2, corresponding to a fluctuation exponent α=1,5. Therefore, the SP process recorded at Urla Station is a random walk process generated by independent "Brown noise" inputs, and can be modeled as a "fractional Brownian motion(fBm)". Furthermore, in a visual basis, the possible relations between the SP time series data and the timings of earthquakes (ML≥3), and between the total daily precipitations at nearby stations supplied from MGM and subsoil temperatures measured at the Urla Station are investigated. When the SP data compared with the earthquake magnitudes, there is no a clear relationship between them, but it is observed that the subsoil temperatures and precipitation data played an active role on SP anomalies. This result is evidence that SP is dependent on seasonal effects. It shows that the streaming potential measured in the area are due to infiltration and that the abundant fracture unconfined aquifer feature, Kocadağ volcanics are affected by the surface effects. It shows that Kocadağ volcanics, which featured fractured unconfined aquifer, are affected by the surface infilitrations.