no probs, signed :) Archived Message Posted by Ian M on February 28, 2019, 6:14 pm, in reply to "Save Sherwood Forest from fracking" Also, twitter thread explaining the discrepancies of magnitude: Brockham Oil Watch ‏ @BrockhamWatch @BGSseismology @seismo_steve Could you clarify why yesterday’s earthquake was reported in the media as anything between 3.0 and 3.7 ML? Why such large discrepancy? People are describing this tremor as stronger than the one in July 2018 also reported as 3.0 ML. 5:32 PM - 27 Feb 2019 The daily mail reported it as 3.7 originally (seems it was later revised), but they also seem to have the location wrong.. https://www.dailymail.co.uk/news/article-6750027/Gatwick-Airport-area-hit-earthquake.html?fbclid=IwAR133gRM3ohqO-vyP3tbIK8fIAGrL8RAz2hIAASL5Rfg951y1sRyUy3HOLY … Stephen Hicks ‏Verified account @seismo_steve 11h11 hours ago Replying to @BrockhamWatch @BGSseismology That's a good question. Will take a few tweets to answer. The initial estimate of ML3.6 (not 3.7) came from the European monitoring agencies using seismic stations located quite a long way from the earthquake, so already that adds some error due to earthquake location uncertainty 2 replies 0 retweets 1 like Stephen Hicks ‏Verified account @seismo_steve 11h11 hours ago Also since ML = "local magnitude", there are some subtle, region-specific differences compared to the traditional Richter scale (designed for California). This is due to different geology etc. Monitoring agencies in different countries compute ML in a slightly different way. 1 reply 0 retweets 1 like Stephen Hicks ‏Verified account @seismo_steve 11h11 hours ago The European-Meditteranean Seismological Centre (@LastQuake) since revised their estimate down to ML 3.3 once they had received additional data and done the re-analysis. The difference this and ML3.1 (BGS) is due to slight variations in the different ML scales used. 1 reply 0 retweets 1 like Stephen Hicks ‏Verified account @seismo_steve 10h10 hours ago The reason why we should use the BGS estimate is that it uses data from the 5 temporary local monitoring stations we installed, and more importantly it is consistent with the previous events in the Surrey quake sequence and other events in the UK so we can make direct comparisons 1 reply 0 retweets 1 like Stephen Hicks ‏Verified account @seismo_steve 10h10 hours ago Your point about the reported felt intensities and the perception of the event is interesting. One possible explanation is that there was a difference in location or faulting mechanism between yesterday's event and the ML 3.0 quake on 5 July last year. But that seems unlikely. 1 reply 0 retweets 1 like Stephen Hicks ‏Verified account @seismo_steve 10h10 hours ago My best explanation was that the 07/05/18 M3.0 event occurred in the middle of the day - when people are more likely to be up and about doing things. That can result in a slightly reduced feeling of shaking intensity. 2 replies 0 retweets 0 likes Stephen Hicks ‏Verified account @seismo_steve 10h10 hours ago Whereas lying down in bed at night (you're more likely to feel the ground shake in that position) when everything else is quiet, and then suddenly being shaken and woken up might be perceived as a slightly higher shaking intensity. 1 reply 0 retweets 1 like Stephen Hicks ‏Verified account @seismo_steve 10h10 hours ago Regardless, the current estimates of ML 3.1 for yesterday’s event makes it the largest event of the seismic sequence so far ... so that will have likely resulted in producing the strongest ground motions yet. 2 replies 2 retweets 3 likes New conversation Brockham Oil Watch ‏ @BrockhamWatch 4h4 hours ago Thank you very much for the explanations. It would also be interesting to know whether @BGSseismology observed a noticeable difference in the number of reports of the July quake vs last night. Message Thread: Strongest earthquake yet in Surrey 3.42 this morning - Ian M February 27, 2019, 3:03 pm Letter in The Times - Ian M February 27, 2019, 6:51 pm Thanks Ian... - Gerard February 28, 2019, 1:23 pm Save Sherwood Forest from fracking - Gerard February 28, 2019, 2:39 pm no probs, signed :) - Ian M February 28, 2019, 6:14 pm Ditto nm - Tomski February 28, 2019, 6:50 pm background of 'geoscientists' in favour of relaxing traffic light system - Ian M March 1, 2019, 12:34 pm video interviews of residents - Ian M March 1, 2019, 7:36 pm   Searching