Practical Local Magnitude Calculation for Local Networks

In this study, we developed a Matlab application (Ml_Calc) to calculate local magnitude (Ml) for small institudes which has just one or more seismic stations. Ml_Calc algorithm suitable for velocity or acceleration sensors' data obtained by Güralp Systems digitizers. The selected earthquake data can be transferred from SCREAM software to Ml_Calc online or offline. The Ml_Calc algorithm provides two types of solutions for distance, one of them is P-S time differences and the other one is epicentre of earthquake and station coordinates, if earthquake is known. During Ml calculation, instrument correction has been removed and converted to real displacement in milimeter. The obtained displacement data converted to Wood Anderson Seismometer output by using Z=[0;0]; P=[-6.28+4.71j; -6.28-4.71j]; A0=[2080]. Obtained maximum displacement amplitude (A) and distances (dist) used in formula (1) for distances less than 200km and formula (2) for more than 200km. Ml=log10(A)-(-1.118-0.0647*dist+0.00071*dist2-3.39E-6*dist3+5.71e-9*dist4) (1) Ml=log10(A)+(2.1173+0.0082*dist-0.0000059628*dist2) (2) Ml_Calc is a software that easy to implement, can be used for educational purpose and user friendly. Due to this characteristics, Ml_Calc software offered a practical solution to individual users to Ml calculation.