Here's an analysis of the concordance lines for "fathom," organized into nine sections as requested.

1. Collocates
Frequent words appearing near "fathom" include: can't, could, not, hard, difficult, even, begin, why, how, what, little, just, really, fully, never, psychology, nature, always followed by 'to'. The negative forms (can't, could, not) are very prominent. Adjectives like hard and difficult are also common.

2. Semantic Prosody
"Fathom" often carries a negative semantic prosody, suggesting difficulty, impossibility, or incomprehension. The frequent use of "can't," "couldn't," "hard to," and "difficult to" reinforces this negative association. It suggests a struggle to understand or grasp something.

3. Register & Formality
The register appears to be quite varied. While some instances occur in relatively formal writing (e.g., discussing economics, political violence), many others are found in informal contexts (e.g., personal blogs, conversational dialogue). The phrase "can't even fathom" leans towards a more informal, emphatic style.

4. Phraseological Patterns
Common phraseological patterns include: can't fathom, couldn't fathom, hard to fathom, difficult to fathom, begin to fathom, even fathom. These patterns often express an inability or struggle to understand something. Fathom out appears once.

5. Grammatical Patterns
"Fathom" is primarily used as a transitive verb. It's frequently followed by a that-clause or a wh- clause (why, how, what) functioning as the object of the verb. It also appears in infinitive constructions (to fathom).

6. Recurring Sentence Structures
A common sentence structure is: [Subject] can/could [not/never] fathom [object clause]. This highlights the subject's inability to understand the object of the verb. Another structure is It is [adjective] to fathom [object clause], where the adjective expresses the degree of difficulty.

7. Pragmatic Function / Discourse Role
"Fathom" often serves to express the speaker's or writer's lack of understanding, disbelief, or confusion. It can be used to convey surprise, frustration, or a challenge to the reader or listener to explain something. It can also be used for emphasis, particularly with "can't even fathom."

8. Frequency & Dispersion
The frequency is relatively high within the given sample (100 lines). The dispersion seems broad, appearing in news articles, blog posts, fiction, and transcribed speech, suggesting it's not restricted to a specific genre.

9. Thematic Context (Topics)
Recurring themes include: politics, human behavior, emotions, abstract concepts, complex situations, and personal experiences. The word is often used when discussing difficult or perplexing aspects of life, society, or the world.