Magnitude determination using cumulative absolute absement for earthquake early warning
Yih‐Min Wu, Himanshu Mittal, Yueh-Ho Lin, Yu‐Hsuan Chang
Abstract
Abstract The cumulative absolute absement (CAA) of the 3 s window after P-wave arrival can be used to estimate the magnitude ( $${M}_{CAA}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>M</mml:mi><mml:mrow><mml:mi>CAA</mml:mi></mml:mrow></mml:msub></mml:math> ) of an earthquake. This method can achieve good results even when only the six stations nearest to the epicenter are used. The standard deviation between the estimated CAA magnitude ( $${M}_{CAA}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>M</mml:mi><mml:mrow><mml:mi>CAA</mml:mi></mml:mrow></mml:msub></mml:math> ) and the moment magnitude ( $${M}_{w}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>M</mml:mi><mml:mi>w</mml:mi></mml:msub></mml:math> ) is found to be 0.3 when using either 6 or 20 stations. This means that $${M}_{CAA}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>M</mml:mi><mml:mrow><mml:mi>CAA</mml:mi></mml:mrow></mml:msub></mml:math> can be reliably predicted using the closest 6 stations. On the other hand, the magnitude ( $${M}_{Pd}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>M</mml:mi><mml:mrow><mml:mi>Pd</mml:mi></mml:mrow></mml:msub></mml:math> ) derived from $${P}_{d}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>P</mml:mi><mml:mi>d</mml:mi></mml:msub></mml:math> using the closest 20 stations has a standard deviation of 0.4 between the estimated $${M}_{Pd}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>M</mml:mi><mml:mrow><mml:mi>Pd</mml:mi></mml:mrow></mml:msub></mml:math> and $${M}_{w}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>M</mml:mi><mml:mi>w</mml:mi></mml:msub></mml:math> . This suggests that CAA is a better magnitude determination parameter for the EEW system than $${P}_{d}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>P</mml:mi><mml:mi>d</mml:mi></mml:msub></mml:math> .