The characteristics (foreshock-aftershock patterns, main shock to the largest aftershock magnitude ratio, and difference in magnitude) of two moderate injection-induced seismicity (IIS) earthquake sequences from Oklahoma, USA, namely, Prague (M 5.7, 2011) and Pawnee (M 5.8, 2016) earthquake sequences, are investigated to comprehend the shallow crustal heterogeneity. The analysis of temporal variation of “b” value from 2002 to 2018 suggests an increase in b-value after 2009. A reduction in b-value after 2016, in response to the reduced injection volumes is noted. A sharp fall in b-value usually precedes the main shocks of magnitude M ≥ 3.5. The foreshock b-values are lower than the regional b-value and aftershock b-values are higher than the regional b-value within the error limits. The investigated earthquake sequences fall under Type 2 of Mogi’s model. The largest aftershock to main shock magnitude difference of 2, observed for the Pawnee earthquake, could be a response to drastic reduction in injection rates in May 2016. The characteristics of ISS observed at Oklahoma are similar to the observations from the reservoir-triggered seismicity (RTS). However, with multiple injection wells operating from time to time in the region with varying amount of fluids injected, the entire IIS at Oklahoma has an appearance of a swarm.

来自美国俄克拉荷马州的两个中等注入诱发地震活动（IIS）地震序列（布拉格（M 5.7，2011）和波尼）的特征（前震-余震模式，最大余震比的主震以及震级差）研究了（M 5.8，2016）地震序列以了解浅层地壳的非均质性。对2002年至2018年“ b”值随时间变化的分析表明，2009年后b值有所增加。由于注入量减少，2016年后b值有所下降。b值通常会在M≥3.5的主震之前急剧下降。在误差范围内，前震b值低于区域b值，余震b值高于区域b值。研究的地震序列属于Mogi模型的类型2。在波尼地震中观察到的最大余震与主震震级的最大差值为2，这可能是对2016年5月注入速率急剧下降的反应。在俄克拉荷马州观测到的国际空间站的特征类似于由储层触发的地震活动（ RTS）。但是，由于该地区不时有多个注入井在注入不同数量的流体，因此俄克拉荷马州的整个IIS呈群状。